Post tranny tsb mpg/ odometer reading

[gene r]

I'm on my 6th fill up since the tranny update. Combined mpg ( 90 pct hwy 89 oct) 18.1. My guess. I broke even. Maybe lost a few tenths, but better shifting. But I have reason to believe the odometer is off. What do you think?

[MikeT]

Originally Posted by gene r

I'm on my 6th fill up since the tranny update. Combined mpg ( 90 pct hwy 89 oct) 18.1. My guess. I broke even. Maybe lost a few tenths, but better shifting. But I have reason to believe the odometer is off. What do you think?

I beleive you may be correct. VW claims that there is a 4% variance allowed on the speedo and odo.

[csimo]

Odometer accuracy... a sore issue for me. I've dealt with this issue many times.

There is no federal law that defines the accuracy of a vehicle odometer. The closest it comes is CFR Title 49 where it says that a vehicle buyer is entitled to rely on the accuracy of the odometer.

What is the definition of an accurate odometer? Nobody knows since the law is silent. 2% error? 5% error? 10% error? Most manufacturers learned that it's best for them not to define a standard.

Using conventional methods it's virtually impossible to have an extremely accurate odometer. Just one variable, the diameter of the tires change with wear, inflation pressure, temperature, scrubbing, etc. which discounts accuracy. There are many other variables. If you can get within 2% accuracy I think you're lucky, but you might be within 2% this month, and off 4% next month.

In recent years inertial guidance and GPS can improve accuracy, but even these methods have problems. Many GPS receivers have a low sample rate of about once per second. Unless they have an inertial guidance component the receiver assumes you traveled in a straight line since the last sample. This introduces error in itself. Even with an inertial guidance component there have to be assumptions.

I did a quick test about a month ago. I measured one tank using the odometer, OBDII information, and GPS. I didn't bother to document the results, but none of the three agreed. The odometer was the highest number, say 337.2 miles, GPS was next at about 329.4, and OBDII came in at about 325. These were not the exact numbers, but were pretty close for this example. Which one was most accurate? I have no idea to be honest... it was just a fun test to do.

There are few ways to get a truly accurate measure of distance travelled, but the older I get the less it really matters to me.

[Webwader]

I did a comparison test of my odo on a relatively flat section of interstate using the mile markers and GPS. In 100 miles as defined by the markers, the GPS indicated 100.0 miles and the odo 101.5.

[gene r]

Originally Posted by csimo

Odometer accuracy... a sore issue for me. I've dealt with this issue many times.

There is no federal law that defines the accuracy of a vehicle odometer. The closest it comes is CFR Title 49 where it says that a vehicle buyer is entitled to rely on the accuracy of the odometer.

What is the definition of an accurate odometer? Nobody knows since the law is silent. 2% error? 5% error? 10% error? Most manufacturers learned that it's best for them not to define a standard.

Using conventional methods it's virtually impossible to have an extremely accurate odometer. Just one variable, the diameter of the tires change with wear, inflation pressure, temperature, scrubbing, etc. which discounts accuracy. There are many other variables. If you can get within 2% accuracy I think you're lucky, but you might be within 2% this month, and off 4% next month.

In recent years inertial guidance and GPS can improve accuracy, but even these methods have problems. Many GPS receivers have a low sample rate of about once per second. Unless they have an inertial guidance component the receiver assumes you traveled in a straight line since the last sample. This introduces error in itself. Even with an inertial guidance component there have to be assumptions.

I did a quick test about a month ago. I measured one tank using the odometer, OBDII information, and GPS. I didn't bother to document the results, but none of the three agreed. The odometer was the highest number, say 337.2 miles, GPS was next at about 329.4, and OBDII came in at about 325. These were not the exact numbers, but were pretty close for this example. Which one was most accurate? I have no idea to be honest... it was just a fun test to do.

There are few ways to get a truly accurate measure of distance travelled, but the older I get the less it really matters to me.

My odometer was dead on before the tsb mod. How do I know? I have gotten gas in the same station for twenty years, clear the trip odometer then drive home. Every car I have ever owned read 2.1 miles from station to drive way including the RL. Since the tsb mod it has been reading 2.4. Thats significant

[MikeT]

Originally Posted by gene r

My odometer was dead on before the tsb mod. How do I know? I have gotten gas in the same station for twenty years, clear the trip odometer then drive home. Every car I have ever owned read 2.1 miles from station to drive way including the RL. Since the tsb mod it has been reading 2.4. Thats significant

Three tenths of a mile difference on a two mile trip is quite a bit different. Anyone who has the shop manual. Please explain how the odo on the Ridge works. All of my previous vehicles had mechanical gears involved for the odo (At least I thought they did). I too have noticed a difference between my odo and GPS, but as csimo stated, the gps sampling rate could cause this. But I did not pay attention to it before the trany update.

[ChrisM]

Originally Posted by gene r

My odometer was dead on before the tsb mod. How do I know? I have gotten gas in the same station for twenty years, clear the trip odometer then drive home. Every car I have ever owned read 2.1 miles from station to drive way including the RL. Since the tsb mod it has been reading 2.4. Thats significant

If what you are saying is correct, your odometer will read 112,500 miles when it only has 100,000 acutal miles.

That is a huge difference. A 2%-4% error is acceptable. 12.5% isn't.

[Webwader]

Please explain how the odo on the Ridge works. All of my previous vehicles had mechanical gears involved for the odo (At least I thought they did).

I don't know how the odo on the Ridge works, but with an electronic display, it obvisously is no longer mechanical at some point. I do know that the recording of mileage is after it becomes an electrical signal. When I had the fuse blow in my dash (#21, under-dash fuse box), the odo reading when the problem was fixed was still at the mileage that it had failed at.

[arteegee]

Originally Posted by gene r

My odometer was dead on before the tsb mod. How do I know? I have gotten gas in the same station for twenty years, clear the trip odometer then drive home. Every car I have ever owned read 2.1 miles from station to drive way including the RL. Since the tsb mod it has been reading 2.4. Thats significant

Mine too was dead-on before...haven't checked it since. Yes, that is quite a significant difference.

[geotech]

Originally Posted by arteegee

Mine too was dead-on before...haven't checked it since. Yes, that is quite a significant difference.

For me, dead-on before and after the update. No change.

The best way to easily check your speedometer is to clock with a digital watch/stopwatch between mile markers on interstate highway. I know that as a rule, they are very close. Set cruise control to a certain speed, say 70 mph. You clock 52 seconds between mile markers. From the chart, that corresponds to just a little over 69 mph. The pdf file is the same chart.