axleaddict.com/cars/ Is-E15-Ethanol-Bad-F or-Your-New-Cars-Eng ine-Lets-Reviewwww.ethanolrfa.org/r esources/blends/e15/www.snopes.com/fact- check/e15-gasoline/some of these links might help im not sure what car you drive but since it is a flex fuel you will probably be okay at worst if you had done it by accident i would just fill up with the proper fuel. i believe the difference has to do with the amount of ethanol in the gas. id think using e15 in a non flex fuel car over time could damage it. this could be different with specific cars like my vette has been tuned specifically for 93 octane so using a lesser fuel might be more likely to damage it but in a stock flex fuel car i wouldn't worry too much if it accidentally happened

I have a GMC truck, I did notice the gas gauge did not move to full even though I put a full tank. I called the GMC dealership and he said the same thing that it should be fine. With these gas prices I thought I would go with the E85 since its a bit less expensive

@ferocious : different fuels may get u different mpg regardless of full tank or not. i would def see whats more efficient i wonder if the different density or something in the fuel causing it to show less then a full tank. over in the vette world we switch to e85 for the horsepower gain because tuners can add more timing since e85 burns cooler.

Stupid question, what the heck are y'all talking about

Flex fuel means you can use either. E85 is 85% ethanol and E15 is 15% ethanol. Your engine is made to run on 0% ethanol but has been adapted to run on ethanol which is lower octane so you have to burn more of it to get the same amount of energy so even though E85 is cheaper you will negate the savings because your miles per gallon goes way down. So your better off using traditional gasoline. "Due to ethanol's lower energy content, FFVs operating on E85 get roughly 15% to 27% fewer miles per gallon than when operating on regular gasoline, depending on the ethanol content. Regular gasoline typically contains about 10% ethanol."

www.fueleconomy.gov/ feg/ethanol.shtml

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@Sophie1 : what kinds of gas are okay to put in your car

@krpen71 : Excellent explanation. I learned so much. Thanks! You seems like a great expert! Again thanks

@krpen71 : thanks, I learn something new every time I am on this site