What Octane do you use?

I know this has been done but let's get some statistics.

I use whatever regular unleaded is (87 or 89). I'll vote after I get gas next time to see what it.

Swamp its 87.

Swamp its 87.
That's what I thought, but wasn't sure.

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I know this has been done but let's get some statistics.

I use 87. I've noticed (on the road) that many stations offer 87 and 89 at the same price, however the 89 is ethanol enhanced.

Don

Bump to the top. A little more than 1000 miles on my Ridgeline and all it has ever drunk is 87 octane Chevron.

should have made this a sticky.

I have always found the higher octanes made my vehicles run smoother! 91

IMHO, the only cars that really need the higher octane are '60s musclecars. As a side note, I've owned two 1990 Jaguar XJ6's that were labelled saying to use only premium, but following the advice of the Jaguar forum I used to frequent, tried and kept using 87 octane. I still have one of the Jag's now. No detonation/backfiring/hesitation. Always passes smog checks and has plenty of power. I just mention the Jaguar because a lot of people are under the false impression that upscale vehicles would require more expensive gasoline. Not really so.

IMHO, the only cars that really need the higher octane are '60s musclecars. As a side note, I've owned two 1990 Jaguar XJ6's that were labelled saying to use only premium, but following the advice of the Jaguar forum I used to frequent, tried and kept using 87 octane. I still have one of the Jag's now. No detonation/backfiring/hesitation. Always passes smog checks and has plenty of power. I just mention the Jaguar because a lot of people are under the false impression that upscale vehicles would require more expensive gasoline. Not really so.

Not upscale vehicles, but higher compression engines require higher octane fuel. Most any EFI engine can compensate for a lower octane fuel by retarding the timing which intern lowers the gas mileage and power.

I always use regular unleaded, 87, but when in higher altitudes such as in Nevada and Utah the regular went down to 85, so I used the premium 87 or 88 octane because the book says to use at least 86, I think. Got real good mileage on that long trip, too, 21-22mpg.

IMHO, the only cars that really need the higher octane are '60s musclecars. As a side note, I've owned two 1990 Jaguar XJ6's that were labelled saying to use only premium, but following the advice of the Jaguar forum I used to frequent, tried and kept using 87 octane. I still have one of the Jag's now. No detonation/backfiring/hesitation. Always passes smog checks and has plenty of power. I just mention the Jaguar because a lot of people are under the false impression that upscale vehicles would require more expensive gasoline. Not really so.

Depends on what you mean by "need".
As already mentioned, most vehicals today have knock sensor which will compensate for lower octane by retarding timing. But by doing so, cars whose ECU's were programmed for higher octane will lose performance.

Since Ethanol mixed gasoline tends to be cheaper here in the midwest, I've been considering using it in my new (soon to be purchased), Ridgeline. But I wanted to buy it from the get go. I have heard that bouncing back and forth from gas with ethanol to gas without ethanol is not good. However if you stick with Ethanol mix you're OK. I can't remember why the heck they said it was an issue. But that's the latest info that stuck in my pea sized brain. Any thoughts on the matter?

Seriously though, I'm not really all that cheap, I put premium in my Passat because that's what the manual says I should. So I'll put the expensive stuff in if I have to. This just doesn't spec premium so I was going to use ethanol in part for the savings and also to support my local farming community.

A little ethanol is ok as long as it's not E85. Honda specifically states NOT to use E85 or it will void your warranty. Search.

Octane is just the measure of a fuels ability to stay stable under pressure. The common belief that higher octane fuel will give you better fuel economy is wrong... the difference is almost not even measurable, and anyone who says they get better, is making themselves beleive it is worth it. More compression or boost require higher octane, just because the fuel has to stay stable longer during the compression stroke. Use whatever your vehicle says to use. If you use to high an octane, it won't fully burn, and the unburnt fuel will pass through your catalytic converter, plugging it up. The Ridgeline really doesn't need anything more then 87 octane. Sorry for the novel... my bad, and expecially on my first post. :D

If you use to high an octane, it won't fully burn, and the unburnt fuel will pass through your catalytic converter, plugging it up.

Plug up your cat, where do you get that information from? Higher octane will burn smother and cooler than lower octane fuel. The only way it will not burn completely is if the air to fuel mixture is wrong.

Plug up your cat, where do you get that information from? Higher octane will burn smother and cooler than lower octane fuel. The only way it will not burn completely is if the air to fuel mixture is wrong.

Not so sure I buy the cooler part, and the smoother part is also a little questionable. This is my understanding of it, and feel free to point me to corrective information.

The higher octane fuel has the same heat energy as the lower octane fuel, it is just less likely to combust prematurely. If higher octane fuels really burned cooler but allowed for the same or better performance it would make sense to use them in all cars because it would lower the amount of heat pollution caused by vehicle. The reality is that about the same amount of heat is produced regardless of the fuel used. Smoother is more of how it effects the engine. It has less of a propensity for premature combustion and therefore causes engines not to knock, this would cause the engine to run more smoothly but doesn't really impact the burning of the fuel itself.

As to the myth though, you are spot on, the reasoning behind it that I have seen, and there are probably many theories, is that because it burns slower there is the potential with the lower compression vehicles to have started the exhaust stroke before the high octane fuel has completely burned because the fuel was never compressed enough to cause the immediate explosion required to burn off all the fuel quickly.

But if you can point me to somewhere that talks to the cooler and smoother aspect I would be curious.

I've read elsewhere on the net that if you pull a large loaded trailer up mountain roads, that a higher octane can be of some benefit. Is this true?

I've read elsewhere on the net that if you pull a large loaded trailer up mountain roads, that a higher octane can be of some benefit. Is this true?

We found that to be true on our latest trip. Our first trip towing with regular (86?) we only got about 12 mpg. This trip we used premium (91?) and we got about 15 mpg. No noticeable difference in performance but the mileage was better.

The owner's manual states that 87 octane is the ticket except if you are towing, then you need a higher octane rating. The way to tell is if you get any pinging. If you do, get thee to a high octane pump;) . If you have a full tank of 87 and start pinging you can use some octane booster to finish the tank. If you aren't towing and aren't pinging you are wasting money if you use higher octane.

Octane boosters are used to reducing the "ignitability" of the fuel under high compression situations. They also help if the engine is running hot (like when towing). It does NOT increase the "power" of the fuel. It just keeps it from pre-igniting (pinging). You can void your warranty by driving with a continuing pinging problem.

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The way to tell is if you get any pinging. If you do, get thee to a high octane pump;) . If you have a full tank of 87 and start pinging you can use some octane booster to finish the tank. If you aren't towing and aren't pinging you are wasting money if you use higher octane.

I doubt that you would ever get any pinging in the RL. The anti-knock sensors in the engine would compensate by changing the timing and would result in a loss of power, but no pinging.

I use to run on 87 till I tested running on 89 couple of weeks ago. The change in performance was markedly improved. I will be pumping 89 from here on out.:D

Hey, the manual says 87 octane so thats what I use. Besides, it's cheaper!

Hey, the manual says 87 octane so thats what I use. Besides, it's cheaper!
Hi Monte! JMHO, but feeling the engine run smoother (if that's possible!) and more responsive, is worth the extra two dollars more for a twenty gallon fill-up. I'm still tracking my MPG with 89. It seems to have improved, at least on highway. We'll see:) Besides, the manual calls for a minimum of 87, and recommends higher octane for towing...I believe.

I use to run on 87 till I tested running on 89 couple of weeks ago. The change in performance was markedly improved. I will be pumping 89 from here on out.:D
Tex thanks for the info! I ran 89 & this last tank came in at 18.5 city vs my normal 17... that pays for the extra 2 bucks per tank as well as it does seem to have alittle more kick.. perhaps if I didnt punch it so much the mileage would be more:)

I am going to start using higher octane gas as an experiment to see if I get any performance boost. I am also switching to full synthetic oil in about a month, so I want to do the experiment now so analysis of results can be simplified. Thank goodness I can afford whatever it costs to go higher up the octane scale, but I certainly sympathize with those on a gas budget - been there - dont want to go back. While the truck has a bit of pep after it gets going, it certainly falls short of immediate off the line giddyup, which is a needed feature in the stop and go world I travel in.

A buddy at work just brought up a good point that I forgot about!
I will continue to use 89... but need to keep this in mind. In the chicago suburbs, the gas stations buy mostly whatever happens to come in on the docks. BP was supposed to use only their own blend of gas with quality control procedures in place, but here, I have seen genaric trucks refilling their stock. So much for the ole mighty dollar... blows quality right out the door :eek:
Bottom line, if someone finds a station that has reasonble prices, that consistantly gives a good grade of gas... let us know!!
hmmmm what a concept, provide quality, and perhaps the customers will come back:cool:

Around here right now moving to 89 octane for 20 gallons would be $6 difference not $2. There is a 30 cent difference in price. 87 has been dropping fast but the other octane ratings have been way behind. In fact diesel is the most expensive you can buy right now, even higher than 90+ octane ratings. If I commuted with my truck on a regular basis and did a lot of driving I might consider a step up in octane, but for my normal usage it just isn't worth the extra money.

Around here right now moving to 89 octane for 20 gallons would be $6 difference not $2. There is a 30 cent difference in price. 87 has been dropping fast but the other octane ratings have been way behind. In fact diesel is the most expensive you can buy right now, even higher than 90+ octane ratings. If I commuted with my truck on a regular basis and did a lot of driving I might consider a step up in octane, but for my normal usage it just isn't worth the extra money.

Here, where I live in CT, the difference in price between 87 and 89 octane is 0.10 cents.

87 = 2.15 / gal
89 = 2.25 / gal

I've avoided trying hi octane while the gas prices were north of $3. Now that they are back to $2 +/-, I may give a tankful a try. Like the previous post, I don't expect a lot. Of course, I didn't expect a lot when I changed to synthetic oil and I've been pleasantly surprised.

I'm back to 87 Octane. I used 5 fillups of 89 and only once exceeded my
87 octane results and that was a toss up as the increased mileage only offset the increased price. Driveability, no preceived difference. Oh Well:o

I started out with 87 but with a huge drop in gas prices, I've moved up to 91. I did this to see if it would help improve my gas mileage. I'm on my second tank of stright 91. To early to tell yet.

I am on my 5 tank of 89 @ $2.09 and the Ridge runs smoother and has better accelleration. I am also making better gas milage. 15-17mpg in town for the last 3 tanks.:)

IMHO, the only cars that really need the higher octane are '60s musclecars. As a side note, I've owned two 1990 Jaguar XJ6's that were labelled saying to use only premium, but following the advice of the Jaguar forum I used to frequent, tried and kept using 87 octane. I still have one of the Jag's now. No detonation/backfiring/hesitation. Always passes smog checks and has plenty of power. I just mention the Jaguar because a lot of people are under the false impression that upscale vehicles would require more expensive gasoline. Not really so.

I just go by what the manufacturer recommends, my Acura recommends 91 octane, but in Fl we only have 93. I can use 89(mid) but I find it does run better on 93. I haven't used anything but 87 and had no probelms at all. I think if you go by the manufactuer specs you will be fine IMO

Here's something else to think about. Who's going to pay for repairs if you're using better then recommended fuel? Think it's not in issue, then read this.

My other vehicle is a Ford, one day to be replaced by a Honda but for now it's paid for and I'd like to pay off my Ridge a bit before I get into another payment. Anyway, we've been having issues with the fuel gauge not reading the tank level correctly (full vs. empty). We recently took the car in to the dealer for a check engine light and mentioned that in addition, we'd like them to check the fuel gauge (again). They had replaced the fuel sender unit ~6months ago and that was supposed to fix the issue. At that time, they told me it was do to high fulfur content and that I might want to try some other brand of gas. Now, they finally ask me what level of octane I buy and when I say mid/89 they tell me OH NO you're supposed to use 87 and thus your repair wont be covered due to the fact that you're not using the grade of fuel recommended by Ford, as stated in the owners manual. They explained this as, higher octane fuel has a higher sulfur content and thus the system can deal with it. I'm fighting it but I wanted to warn those of you out there, you might want to stick to the regular 87 octane unleaded as stated in your owners manual.

I would be going to a different Service Department for a 2nd opinion on that one. Because that sounds like a brush off if I have ever heard one.

Here's something else to think about. Who's going to pay for repairs if you're using better then recommended fuel? Think it's not in issue, then read this.

My other vehicle is a Ford, one day to be replaced by a Honda but for now it's paid for and I'd like to pay off my Ridge a bit before I get into another payment. Anyway, we've been having issues with the fuel gauge not reading the tank level correctly (full vs. empty). We recently took the car in to the dealer for a check engine light and mentioned that in addition, we'd like them to check the fuel gauge (again). They had replaced the fuel sender unit ~6months ago and that was supposed to fix the issue. At that time, they told me it was do to high fulfur content and that I might want to try some other brand of gas. Now, they finally ask me what level of octane I buy and when I say mid/89 they tell me OH NO you're supposed to use 87 and thus your repair wont be covered due to the fact that you're not using the grade of fuel recommended by Ford, as stated in the owners manual. They explained this as, higher octane fuel has a higher sulfur content and thus the system can deal with it. I'm fighting it but I wanted to warn those of you out there, you might want to stick to the regular 87 octane unleaded as stated in your owners manual.

Get some boots, because you are standing in a pool of BS with that dealer.

Actually you do need a better service dept. I've shared the experience several times.. example I had aftermarket tires that a Chevy dealer told me voided my warranty. Once I showed the blanken* service manager on the net that my tires had the exact factory spec (diameter) than even the ones they were currently selling, he sucked it up and made the repair!
A lower than honorable dealer will do use anything they can to avoid repairs. I found another dealer and they were much better! Shop around, a few handfull of dealers still give a rats A-s about service!

That is the dumbest thing I ever heard of,the higher the octane the better it burns. Deisel fuel is higher in sulphur, but not so with preimum gas. Every one I've talked to seems to agree with that. I burned preimum fuel in my Trooper for 10 yrs. and never had a bit of trouble,they told you that because they didn't know the real answer. The only thing that preimum fuel will effect is your wallet,and possibly your mileage.

I've tried high and regular test....no diff from the drivers seat for me. This truck runs great as advertised without the premium.

Tux, ask them for clarification so that you are sure that you understand exactly what they are telling you. Tell them that you will consider paying for the repair if they put the full text of their reason for declining your warranty claim on the service order. That way you will have them in a corner after catching them in a blatant lie. They won't do it. They will try to find every reason imaginable to get out of documenting their deceptive business practice, possibly fraud. They obviously think that they are pretty good at making stuff up so be prepared to be firm. They either document what they have told you or do the repair under warranty. You have found a business that deserves to be held accountable. Tell everyone that you can about your story. Those folks don't deserve your business or anyone else's. :mad:

I used to own an Audi 3.0. The owners manual called for 91 and that's what I used. I tried 87 but the computer would de-tune the engine for lower octane and I could tell it in acceleration. No other problems, though. I did this after break-in at about 40k miles.
91 octane = 6.7/6.8 sec. 0 to 60
87 octane = 7.2/7.3 sec. 0 to 60

My Ridge is far (145 miles, 2 weeks ;)) from break-in, so I can't do these comparisons. I could check my milage, but I really don't care. It's not, after all, a mini. ;)
Anyway, I work at Chevron research in CA and I've asked labrats and chemists about octane because there's so much deeply imbedded mis-information out there. The consensus is that you should use whatever octane your manual reccommends. Some engines adjust, some do not. My old Ford Windstar 3.7L, for example, gave the specs for the range of octanes, with different HP ratings for each.
BTW; all gasolines are not the same. They differ mostly in detergent compounds. According to two mechanics I trust, one a performance tuner, Techron rocks. Both agree that if you use cut-rate you should add it every tankful. But these are guys who really like cars.
Does that diatribe answer the question? :eek:
Sorry, I do go on.

Hmmmm...Chevron dudes recommending Techron? Not really a surprise, but your point is a good one regarding the detergents and other additives. I fill up at one of the discount wholesale stations, but every fourth or fifth tank get some 'real' gas. I have experience of the refining industry in the UK and have seen the cross supply of fuel between the major brands before they add their specific additives. And they say there's no cartel :rolleyes:

Hmmmm...Chevron dudes recommending Techron? Not really a surprise, but your point is a good one regarding the detergents and other additives. I fill up at one of the discount wholesale stations, but every fourth or fifth tank get some 'real' gas. I have experience of the refining industry in the UK and have seen the cross supply of fuel between the major brands before they add their specific additives. And they say there's no cartel :rolleyes:
Actually, the two dudes who recommended Techron are not Chevron. One's a mechanic I took my previous cars to, and the other's the owner of Griffin Motorwerke here in Berkeley who worked on my A4.
The Chevron dudes recommended using the octane specified in the manual. They do, though, stand by Techron as a quality product. They say that raw gas, before additives, is indeed pretty much the same within the octane ratings.
You must know that some employees of a company revel in dumping on that company's product. You should hear us talk about the toy cars. :p
I'm a proud owner of Travis Tanker myself. Mind that envy now.

The manual actually states:
"Towing performance can be affected by high altituide, high temperature, or when climbing steep grades. Therefore, premium fuel is recommended when towing more than 3,500 lb (1,500 kg)."
The RL should not ping under any conditions as it has knock sensors and electronically variable timing. The recommendation is there because by using higher octane fuel, the timing will advance more, thus producing more horsepower. The only time this will occur is under a heavy load, which is why using premium fuel in normal driving conditions will not yield higher gas mileage.

Ah, yes, the dreaded CRS. It seems to run rampant in us older folks. :)

At altitude here the regular is 85 octane and the truck runs well on it. In fact has told the dealers here to only suggest the 85 octane. Unless a vehicle is pinging or running rough you are only wasting money paying for higher octane fuel.

Didn't Consumer Reports do a performance test on vehicles using different octane gas. I seem to remember the Accord sedan used in the test performed better on 85. I'm sure someone out there know what I am typing about.

Mike do you have 85 octane there, the regular in Houston is 87?

Like jeffpajap above, 85 is regular at this altitude and was recommended by the dealer.

Roak

87 for daily driving...91 for the roadtrips.

87 is the lowest octane available in my area but it costs over $3.59 a gallon. Once out of town I tried 91, because it was cheaper. Not much difference from my pov, so it's back to 87.

I run 91.
Theres about a .20 cents a gallon difference from 87 to 91 that works out to around a extra $4.00 bucks a fill-up, well worth it for me to run the 91 all the time.

I use 85. That's regular grade where I live (at 7500 feet), and premium would probably run poorly up here unless you have high-compression heads (in which case, the owner's manual would tell you to use premium).

I also have a Honda ST1100 motorcycle. I run 85 in that, too... ;)

I run 91.
Theres about a .20 cents a gallon difference from 87 to 91 that works out to around a extra $4.00 bucks a fill-up, well worth it for me to run the 91 all the time.

Same here, 93 octane since day one. Flip flopping between grades now and then will not make much difference. The computer will take time to readjust the timing to take advantage of the octane difference.

The owners manual says to use regular; so that's what she gets!

DoctorJ; I could not help but to notice that picture of one sweet ride!!! :D

Bump to the top. A little more than 1000 miles on my Ridgeline and all it has ever drunk is 87 octane Chevron.

700 miles and 87 octane, that's all:D

I still use 87, but every 6 months when I add a bottle of techron into the system, I fill up with 93 and play dragster on some big hills... :eek:

i use 87 when I can find it. Here in Denver the regular grade is 85 (high content of ethanol). I am surprised any of our cars run.


IMHO big mistake going to ethanol. Sure a few farmers will make some BIG moeny for awhile, but everyone else is suffering because of the big corn prices.

Heard on the radio today that our oil supplies are fine. Some have figured out oil is not produced by aging fossils but something entirely different. I am not saavy enough to know all the details but you can read about the findings here:


Amazon.com: Black Gold Stranglehold: Jerome R. Corsi,Craig R. Smith: Books (http://www.amazon.com/Black-Gold-Stranglehold-Jerome-Corsi/dp/1581824890)


Happy reading.

I've used 89 for years in all my vehicles. Maybe it's psychological but I think it runs smoother.

what i do is i put 89 regular but for long trips i put 92/93 or every 2-3 fill ups it just burns cleaner

Ah, yes, the dreaded CRS. It seems to run rampant in us older folks. :)
According to my wife, it runs rampant in 40 somethings as well :cool:

IMHO big mistake going to ethanol. Sure a few farmers will make some BIG moeny for awhile, but everyone else is suffering because of the big corn prices.
I couldn't agree more. Ethanol and bio-fuels in general are economically disastrous. When food becomes fuel, food becomes expensive. Not to mention the massive amounts of land needed - 1 acre of corn only yields about 330 gallons of fuel, but guess what? It needs about 140 gallons of fuel to harvest that 1 acre! Cornell University did a study a while back that figured it takes 70% more energy to create a gallon of ethanol than it produces. It makes no sense.
BTW - so not to hijack the thread - I use 87 octane. No point in using anything else imho.

Last week I measured my economy on a trip from Jersey to Pittsburgh and back; all highway, but very hilly. Heading west, I averaged 19.6 mpg. Heading east, 21.0 mpg. The weather was a little bit warmer coming back, but air pressure and wind were of little effect. Heading west I was burning 87 octane, and coming back 89. I don't know if that was the difference.

What is notable is that when gas was $1/gallon, that 89 octane cost 10-15% more. Now with gas closing on $4/gallon, going up a grade only costs 2-3% more. This equates to only a .5mpg improvement required to justify the cost.

Mostly 87.....then on holidays (hee, hee).....89! I switch off every now and then....depends on how much "mean green" I have in my pocket!

I also only use 87, no sense paying more if you don't need it. Now when towing or doing a lot of hauling I might spring for the 89 or 91, but typically not.

87. Do they make a 50 octane - then perhaps they could sell it for only $3.00 a gallon? :rolleyes: What is really sad, is that I said "ONLY" $3.00 a gallon - and meant it.

IMHO, the only cars that really need the higher octane are '60s musclecars. As a side note, I've owned two 1990 Jaguar XJ6's that were labelled saying to use only premium, but following the advice of the Jaguar forum I used to frequent, tried and kept using 87 octane. I still have one of the Jag's now. No detonation/backfiring/hesitation. Always passes smog checks and has plenty of power. I just mention the Jaguar because a lot of people are under the false impression that upscale vehicles would require more expensive gasoline. Not really so.

There's some generalizations in this that might lead people to think that running low grade fuel in their cars is okay. Not really so. However, it CAN be done.

Muscle cars did have "high" compression for their day, but new cars all have fairly high compression by 70's and early 80's standards and equal to or is higher than the peak of the muscle car era. Those old V8's did need high octane fuel to prevent pre-igntion. This was partly due to poor engine design and poor fuel delivery (carbs). High octane, in effect, is a great band-aid.

Any late model car will adjust (read: retard) the ignition timing to work with the low octane gas. This will result in loss of power and reduced throttle response. The Jaguar may not be effected much and if memory serves me, don't have very high compression (no more than 10:1). It also might be that Premium is recommended to help better protect from potential pre-igntion problems. Back then (1990) the additives in fuel might have been different for Premium than lower grades of fuel. Hard to say what Jaguar was exactly thinking.

Anyway, speaking from personal experience, if it's summertime and the car calls for Premium, that's what it gets. When it cooler, and the car isn't being driven hard, or on a long trip, one grade lower is used to save $. Highway driving does not put much load on an engine.

I would not say to anyone, that it's okay or safe, or recommended to use low octane fuel. Every car is different, but there is an element of risk.

If one takes the time to read the RL manual, I believe there's a recommendation to use Premium gas when towing 3500lbs or more. Basically this tells me that for optimum performance the engine can and will benefit from more octane, in addition to extra protection provided from higher octane.

I've yet to try this test: read the live data (via a scanner) for Timing Advance with both 87 and 92 octane fuel. Currently the RL has 92 in it......my guess is there will be a noticeable difference.

DID SOME SERIOUS RESEARCH A WHILE BACK AND CAME TO THE FOLLOWING CONCLUSION: Keep in mind these are layman terms and kept as simple as possible for the sake of explanation.

All gas when first refined is the same octane. It all stores the same energy.

Octane is basically a means of controlling the ignition rate (stability) of the gas. The fuel doen't actually explode in the chamber, it just lights and burns really fast.
But for sake of simplicity let's call it Explosion.

Raw untreated gas will ignite extremely fast. If used in that state the engines would have to have extremely low compression and serious cooling to keep from Pre-Igniting that gas. They experimented with ways to slow the igniting of the gas and found lead to be the least expensive way to go. The more lead, the higher the octane and the slower the "Explosion" which is not really an explosion, but a convenient term to use. Amoco developed fuels without lead. They used something else and their "White Gas" was more expensive. Of course, eventually every manufactures went the same route.

High octane fuels have the same energy level as low octane fuels. They just "Explode" slower.

A high octain gas can run with more ignition timing. This means the plugs can fire earlier on the compression stroke.

The numbers aren't exact but just used as example. A performance type engine may run it's best if the plugs fire 10% before the piston reached the top of the compression stroke. And that will vary with load requirements. If the gas explodes too quick, the piston recieves a jolt while it is still coming to the top, and it is being pushed to go back down backwards. This results in a knock or pinging sound and is not good for the top of the piston or connection rods bearings. When modern engines "hear" this, the ECU retards the spark timing to say Top dead center instead of 10 degrees before TDC. So that the explosion is driving the piston down when it is supposed to be going down. That is what happens when 87 is used in a modern car designed for 91 octane.

If 91 was used the Explosion would have been slower and the piston would have reached the top and started back down before the jolt hit it. So spark timing would have been left in its nornal state.

With engines designed to run on 87 octane, the optimum spark timing is also set to fluctuate with the various load requirements. But all the timing is at a more retarted state than for a performance engine. As with the above, if it hears a knock or ping, the timing will be retarted to compensate. This would be most likely to happen in heat and towing a heavy load up a mountain. These condition could cause the combustion chamber to get much hotter than normal driving would and the extra heat might result in the lower octane to pre-ignite.
So 91 octane, would be in order as it "Explodes" slower, keeps the ping at bay and the ECU doesn't have to retard the timing.

However under most all driving condition the timing is doing its thing and is happy because it doesn't "hear" any problems. If high octane is used, the engine still "hears" no problems and it is happy with it's settings. It doen't advance the timing to dance the tune of the high octane. The plugs are firing and igniting a slower burning high octane than the quicker burning lower octane that they were supposed to ignite.

All that to say this:

High octane has no more stored energy than low octane. It is not more powerful! It just "Explodes" slower. MORE STABLE!

High octane will get no better fuel mileage in an engine designed for low octane. Except in extremely heavy Load Conditions.

High octane may result in lower MPG because of its slower burn rate.

High octane may contain more or better cleaning additives.

I get better mileage with Shell 87 than any other gas I've tried and don't have a clue why! :confused: :eek:

Kip

KipK... Thanks for your thoughts... I also always get better fuel economy on Shell products. I however, will disagree with your statement that higher octane will not provide better fuel economy. Every time I run higher octane fuel, I always obtain better fuel mileage both for city and highway driving. This is due to higher octane fuels has less ethanol... In the state I reside 87 octane contains 10% ethanol.

First, I'm with xridgelinex on Shell gas. I probably burn more Chevron, simply because the Chevron station is closer to my house, but I've found Shell typically gets 1-1.5 mpg better fuel economy on the same grade. This holds true for our Pilot as well as the Ridgeline. Recently, my wife was in a pinch & put Exxon in her Pilot, dropped 2 mpg off her usual mixed driving average. In both vehicles, running Shell 93 octane is worth an extra 2 mpg over 87 octane & 3 mpg over 87 octane Chevron.

X's observation about ethanol content in 87 octane is also correct. (I might add that I read in the paper that the local Chevron refinery buys most of its ethanol from Brazil. So much for ethanol helping us with "energy independence" ;))

If I know I'm going to be knocking around town with little highway mileage, I tend to just run Chevron 87 octane because it's a lot cheaper. But if I'm heading out on a highway run - Shell 93 octane. The performance difference, particularly less downshifting on long grades & more "ECO" time in the Pilot, is easy to observe.

First, I'm with xridgelinex on Shell gas. I probably burn more Chevron, simply because the Chevron station is closer to my house, but I've found Shell typically gets 1-1.5 mpg better fuel economy on the same grade. This holds true for our Pilot as well as the Ridgeline. Recently, my wife was in a pinch & put Exxon in her Pilot, dropped 2 mpg off her usual mixed driving average. In both vehicles, running Shell 93 octane is worth an extra 2 mpg over 87 octane & 3 mpg over 87 octane Chevron.

X's observation about ethanol content in 87 octane is also correct. (I might add that I read in the paper that the local Chevron refinery buys most of its ethanol from Brazil. So much for ethanol helping us with "energy independence" ;))

If I know I'm going to be knocking around town with little highway mileage, I tend to just run Chevron 87 octane because it's a lot cheaper. But if I'm heading out on a highway run - Shell 93 octane. The performance difference, particularly less downshifting on long grades & more "ECO" time in the Pilot, is easy to observe. I do agree with this for some strange reason. I did not check gas mileage a few yrs ago when I did it but the less down shifting when on highway with the Shell premium. I posted this around the time of the 2007 Long Island NY Meet. The truck just seem to run better on that trip & tank of gas. I put WAWA premium in it when I left Southern Maryland & got some more premium Shell when I got to the Maryland House over 100 miles away. I use premium fuel all the time in my Acura that is what is required. The Ridgeline mostly get the regular gas but it was strange the way the truck ran compared to other times with highway trips.

I will leave out my opinions, because everyone has them and they are not always based on fact.
Here's the facts;
one tank full, run from full to just above empty. 87 octane gave me 16.3 MPG combined (daily driving)
Next tank full, also full to just before empty. 91 octane gave me 17.4 MPG combined (daily driving)

Also, better "feel in my seat" driving impression.(i.e.: felt better performance) very subjective, but there nontheless.

both times, obviously, you have to take into account residual effects.

just my two cents,

Liam

The best effect or change that I've ever noticed with different gas was on a 1994 Nissan Pathfinder. It had the anemic V6, luckily with the 5spd manual trans.

When I was commuting to school over a sizeable hill, it always had to work hard. Town driving was also a hassle, even keeping up with traffic. Other than that the engine ran well.

After trying 92 oct. fuel it made a noticeable difference. Slightly better torque and power.

I thorized that it would be safe to advance the timing. It's been years but it was something like 3 to 5 degrees more. The improvement was impressive with much better bottom end torque and generally better power. No pre-ignition.

The best part was despite the extra cost of premium fuel, the MPG was improved enough to offset the cost. In fact it came out slighly ahead and made it fun to drive.

Of course on newer cars the computer manages timing and the effect will vary. The most obvious change that I noticed was on a late model Audi A4 V6The car just languished with 87 and felt very slow, but once the "complimentary" dealer provided tank was used, in went 92 (as recommended). It was night and day between the two octane ratings. I think the German cars are pretty sensitive. The A4 had about 10.3/1 compression, where my last Audi V8 had 11.1/1 and never used anything but 92. Wasn't willing to save $5 of gas on a $55K car!

KipK... Thanks for your thoughts... I also always get better fuel economy on Shell products. I however, will disagree with your statement that higher octane will not provide better fuel economy. Every time I run higher octane fuel, I always obtain better fuel mileage both for city and highway driving. This is due to higher octane fuels has less ethanol... In the state I reside 87 octane contains 10% ethanol.

I agree with your observations when comparing 10% ethanol fuels with 100% "dino" fuels. My statements were based on the fuels being the same except for the higher octane of one over the other.

On other forums the posters have reported +10% and better mileage with 87 octane dino vs 87 octane ethanol blend. However when comparing 91 and 87 octanes with the same (or lack of) ethanol, no difference was observed. But like I said above, the more expensive fuels may contain better cleaning agents.

Unfortunately the Shell pumps in our area have a label that reads: "May contain up to 10% ethanol". This would indicate that all 3 grades coming from that pump would contain ethanol.

Some of the poster have reported 1-3 mpg higher with premium fuels. And it could very well be because of the differences of dino vs ethanol blend, as in your case. With the Ridgeline that could be 6%-20% better mileage with the premium fuels. If the average price of gas is $2.50 and premium is $2.70, the cost of the premium is 6% to 8% higher and would be well worth the extra price at the pump. But it takes more than a tank here and there to prove that. Other posters have reported no better results with the 91, possibly indicating that they both contain or don't contain ethanol.

My experience has been that even when being as careful as possible, such as always using the same pump and stopping when it shuts off the first time, tank to tank will vary 1-3 MPG under what I "THOUGHT" were the same driving conditions and the same fuel. :eek:

Honda recommends 87 octane except for extreme conditions. I can't imagine why they would want to recommend a grade of fuel that would get 6%-20%less mileage. :confused:

Good debate! FWIW, I'm going to try several tanks of Shell Premium again to see if it makes a difference! It has been a few years since doing that.

Thanks,

Kip

for the last almost 190,000 miles my truck has had all 87 octane, except 1 or 2 tanks of 89 octane when the station was out of 87. Pretty much 3 fill ups a week since January of 2006

From when I bought it til now, I have averaged 19 mpg per tankfull.

just a reference point, I'm not here to debate pros and cons of either, as I am not a mechanic, or chemist, and dont play either on the internet.

Unfortunately the Shell pumps in our area have a label that reads: "May contain up to 10% ethanol". This would indicate that all 3 grades coming from that pump would contain ethanol.


All Shell brand gasoline sold in the USA contains not less than 8% and not more than 10% ethanol. All grades, all states.

For the most part we use 87 octane Unocal 76 gas in the RL. From what I understand it's a Top Tier fuel, which has a stout detergent package. It's our local station, but given a choice like Chevron the best.

However Unocal was closed on T'Giving so filled up at BP/Arco with 92, since it was almost the same price as Unocal' 87 oct. and is the "other" local gas station.

I've tried different types of fuel in the RL and with numerous cars over the years. With the RL, I can't nail down a definite answer on what gas provides the best MPG. Partly, I think, due to my wife, who often runs town errands when the company truck isn't available or she doesn't want to drive it (newer F-150 crew cab). Honestly she hates it....so we pay more for gas since the Honda gets used 3 to 4 days a week.

The biggest factor that effects and increases MPG, and is verified by tracking MPG in a spreadsheet, is longer trips at modest speeds, or taking secondary roads where the speed limit is lower; low speed drastically increases the MPG. Not surprising considering the large hole these trucks punch thru the air.

Someone mentioned getting 19MPG on average; I'm jealous as we're at barely over 16.5mpg, based on a 46 mile highway commute that's basically flat.

All Shell brand gasoline sold in the USA contains not less than 8% and not more than 10% ethanol. All grades, all states.

Thanks Joe! That should make the comparison even more accurate with the only difference being the extra "octane" additives, and possibly some extra cleaners.

Kip

The biggest factor that effects and increases MPG, and is verified by tracking MPG in a spreadsheet, is longer trips at modest speeds, or taking secondary roads where the speed limit is lower; low speed drastically increases the MPG. Not surprising considering the large hole these trucks punch thru the air.

Someone mentioned getting 19MPG on average; I'm jealous as we're at barely over 16.5mpg, based on a 46 mile highway commute that's basically flat.

Yep!

Wind resistance plays a huge part in fuel mileage. Seems the formula is the speed of the vehicle Squared, times the frontal area (FA) of the vehicle. So at 50 mph the wind resistance would be 50 X 50 X FA= 2500XFA.
At 70 mph the resistance would be 4900XFA. Nearly doubled!

We are "stuck" with the FA, but can adjust the speed. :)

Besides a heavy throttle foot, Local driving's biggest enemy are the brakes. The harder they are pressed, the more often they are pressed, and the longer they are pressed results in more wasted fuel.

Kip

I'm jealous as we're at barely over 16.5mpg, based on a 46 mile highway commute that's basically flat.


Is that with the tailgate down?...lol :act060:

Dropped back to 87 yesterday after 2 tanks of 91.;act028: