Changing RD fluid at 10K miles seems excessive, and I’m assuming the maintenance program is calling for the fluid change because the vehicle is now 2 years old, and the program assumes the vehicle would have more than 10k miles.

Nope - your mileage is pretty typical for the B16 code.

See page 494 of the 2023 manual - the first interval B16 commonly pops up around 10K, Honda recommends 7.5k if towing.

 

Change the rear differential fluid.

 

For the 2019-2023 MYs, the MM calls for rear diff fluid change at the 2nd OCI. This is normally about 15K miles. Sounds like the dealer changed the engine oil at 2300 miles (probably because of time, not miles) and reset the MM oil life. Now, ~7500 miles later you’re seeing the B16 code. I would just go ahead and change it now. You won’t see the 6 code for another 30K miles. Curiously, the 2024 and 2025 MMs call for the rear diff fluid change on the first OCI.

 

Curiously, the 2024 and 2025 MMs call for the rear diff fluid change on the first OCI.

Only typically if the first oil change is above 5,000 miles, which most will be. But some are not, including mine, and the '6' code will appear at the second MM oil change code IE B16

 

Here is info compiled by @Wisconsin_Mike

 

You’re all good. I bought mine in March and just hit 7k and mine popped up last week. I had done a little bit of light towing recently so I’m sure that’s why it showed up earlier.

It’s my understanding that they come from the factory with a heavier weight diff fluid that is only meant to be run for the first 5-10k depending on towing so as to basically wear the burrs and what not off the gears in the differential.

 

What is your source for the heavier weight information?

 

I would not try to stretch intervals on preventative maintenance. You may have got away with it on your 2006 but don't push your luck. Especially since it's basically a used vehicle and you have no idea under which the conditions that it wad driven under. Apparently they updated the first diff change to around 5k mi then every 30k mi thereafter. Unless you are towing then replaced the diff fluid every 15k mi.

I bought a demo like yours but mine was under 1k mi. Because technically it was used I didn't get the free oil changes. I was planning on it and it messed up my service plan. I still regret not doing the first oil chg at around 3k mi.

My A16 popped around 6k. My dealer service advisor told me the diff wasn't due but I told them to do it anyway. Do you plan on doing it yourself?