More and more stations around here seem to be switching over to E15 for the mid-grade fuel and at a cheaper price than regular. I put a tank in my big gas-aholic 2000 K3500 just to see if it would affect mileage. Unfortunately I didn’t notice this warning when I did that (noticed it the next time I was filling up).

Is there any reason that E15 would actually cause any damage to an EFI engine? And I assume the “prohibited by Federal law” is due to emissions and the costs of verifying “old” cars running on E15.

Weirdly, my truck seemed to like E15. It seemed to pull better and the mpg difference was within the realm of a rounding error.