# E85 Fuel - Can I add Some in my non E85 Car? **URL:** \ **Category:** Factual Questions\ **Created:** [March 9, 2012, 12:22am UTC](https://boards.straightdope.com/t/e85-fuel-can-i-add-some-in-my-non-e85-car/615213 "2012-03-09T00:22:20Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![JoshuaSD](https://avatars.discourse-cdn.com/v4/letter/j/f1d935/32.png) [@JoshuaSD](https://boards.straightdope.com/u/JoshuaSD)\ **Post date:** [March 9, 2012, 12:22am UTC](https://boards.straightdope.com/t/e85-fuel-can-i-add-some-in-my-non-e85-car/615213/1 "2012-03-09T00:22:20Z")
I know from internet searches that E85 cannot be used repeatedly in a car not designed for it because of corrosion issues. I also read that accidentally filling your tank once should not hurt your car. What I cant find an answer to is this: 1. Will small amounts of E85 added with each fill up of regular gas hurt the car? Let’s say a 9 to 1 ratio. 2. Would I see a fuel efficiency increase, decrease or no change? ---
**Author:** ![robert\_columbia](https://avatars.discourse-cdn.com/v4/letter/r/e79b87/32.png) [@robert\_columbia](https://boards.straightdope.com/u/robert_columbia)\ **Post date:** [March 9, 2012, 12:25am UTC](https://boards.straightdope.com/t/e85-fuel-can-i-add-some-in-my-non-e85-car/615213/2 "2012-03-09T00:25:16Z")
Don’t know about #1, but I have driven a car that is designed to take either regular gasoline or E85, and it gets worse mileage with E85 than with regular gas, so I would presume that you would get worse mileage. ---
**Author:** ![bizerta](https://avatars.discourse-cdn.com/v4/letter/b/3be4f8/32.png) [@bizerta](https://boards.straightdope.com/u/bizerta)\ **Post date:** [March 9, 2012, 1:25am UTC](https://boards.straightdope.com/t/e85-fuel-can-i-add-some-in-my-non-e85-car/615213/3 "2012-03-09T01:25:40Z")
> [@robert\_columbia](#): > > Don’t know about #1, but I have driven a car that is designed to take either regular gasoline or E85, and it gets worse mileage with E85 than with regular gas, so I would presume that you would get worse mileage. The energy content of E85 is 72% that of pure gasoline, so your 29 MPG car is only going to get 21 MPG with E85. Instead of 290 miles on a tankful, you’re only going 210 miles. Of course, the fuel tax is still the same per gallon, so it’s effectively a 39% jump in road tax (per mile). At a Shell station in Charlestown, MA, the E85 price is only 13% lower than the gasoline price, for a net increase of 20% in cost-pre-mile. Anyone who buys E85 with the thought of saving money has not done their homework. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [March 9, 2012, 1:41am UTC](https://boards.straightdope.com/t/e85-fuel-can-i-add-some-in-my-non-e85-car/615213/4 "2012-03-09T01:41:44Z")
1, Most cars these days can handle E15, so if you mix E85 and regular fuel (probably E15 in most areas these days) in a 9 to 1 ratio, the ethanol concentration is still going to be low enough that I wouldn’t expect any major problems from it. 1. Your mileage will definitely decrease, as bizerta’s post explains. I have to ask, though. Why on earth would you think that this would be a good thing to do? ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [March 9, 2012, 2:58am UTC](https://boards.straightdope.com/t/e85-fuel-can-i-add-some-in-my-non-e85-car/615213/5 "2012-03-09T02:58:51Z")
> [@bizerta](#): > > Anyone who buys E85 with the thought of saving money has not done their homework. Unless you’re filling up with E85 before returning a rental car. 🙂 ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [March 9, 2012, 5:58am UTC](https://boards.straightdope.com/t/e85-fuel-can-i-add-some-in-my-non-e85-car/615213/6 "2012-03-09T05:58:09Z")
Is this another alias for the doper that was going to run deisel in a rental car? ---
**Author:** ![JoshuaSD](https://avatars.discourse-cdn.com/v4/letter/j/f1d935/32.png) [@JoshuaSD](https://boards.straightdope.com/u/JoshuaSD)\ **Post date:** [March 10, 2012, 8:58pm UTC](https://boards.straightdope.com/t/e85-fuel-can-i-add-some-in-my-non-e85-car/615213/7 "2012-03-10T20:58:19Z")
Thanks all this is exactly what I wanted to find out. My goal is to maximize the mileage of my 2011 Ford Focus. Through driving adjustments and proper tire inflation I’m up to a stable 35 MPG. I was thinking maybe a little E85 could boost it a few and lower my emissions too. Looks like that’s not the answer though.