Just to put my 2 cents in on this debate. I have run all my vehicles on E-10 and never had an issue. I did do an experment once with my 99 yukon and ran it for half the summer on striaght 87 gas for a 45 days and then switch back to e-10 for the next 45 days and had no mileage differance. averaged 18 mpg the whole summer. I did this because a friend of mine claimed he got better mileage on straight 87. Any way, I get 18 mpg with the yukon, and on a good day (very little wind) 42 mpg with my 98 olds achieva both running on e-10. but, the only thing I do put 87 in is the boat, period. I should put a lead substitue in with it but I dont.