Time for the oil to be changed. Was thinking of switching from 5w20 to 0w20 on my '05 HAH. Have an extended warranty to 100k (I'm now at the 45k mark). Will using 0w20 affect my warranty? Has anyone starting using 0w20, and does it make any difference?
Thanks.

What does the HAH manual recommend? The engine in the HAH is not the same type found in the HCH which requires 0W20 (but 5w20 can be used, but i wouldn't).

I believe the non hybrid accord has the same engine and does NOT require 0W20. I would recommend staying with 5W20 for that engine.

I have some 30k miles on my 05 hah. I of course used 5w-20 and found 0w-20 made no improvement in mpg, except made for a noisier engine at cold startup time.

I also use 10w-30 and found no mpg loss either but noted a much quieter engine at start.

Now that I got it out of my system, and actually tried the various oils, not just read about em, there is no reason to not go back to 5w-20 as recommended by Honda.

They should know best.

To answer the question, I don't know if that'll make any difference in your warranty. However, just to be safe, stick to what the owner's manual recommends: 5W-20. After you hit 100K miles, you can 'experiment' with peace of mind about voiding any warranty. Although, even if you used 0W-20, the dealer would be hard pressed to say that's the reason your engine failed, if it did.

With how reliable Honda engines are, I seriously doubt anyone will suffer any form of engine failure due to using various oil weights, within reason. However, I'd stay away with ultra thick oils, as there are great lengths of small passages in your engine that are designed for a thinner oil to pass through. If you change to say, 20W-50, you *may* not get oil flow to critical areas.

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Mobil 1 Extended Performance 5w-20 and Mobil 1 filter, each changed at 5000 miles.