Running 88E15 gas vs 87E10 in cars - what's the difference??

[Wmoater]

This is definitely not for a spyder. We’re talking cars. I see sheetz has 88 gas with 15 percent E junk in it for 3.99 for this upcoming weekend only. I am pretty sure that’s the stuff I ran out west “one” time and only got half the mileage. So is my thinking wrong? If you fill up with 88 E15 it will take 1.5 fill ups to get the same distance with 87 E10 so you’re actually spending more. Am I correct in this thinking?

[Navydad]

I have no clue as to the ratio of mileage to fill ups, but fuel with more ethanol will give less mileage so you are correct.

[Peter Aawen]

Ethanol has good 'anti-knock' properties & is a great oxygenate which helps to produce a cleaner burning fuel, so it can help boost octane in lower test gas & if your engine can be tuned to take advantage of that, it can contribute to a little increased power that way, but otherwise doesn't really do much for your engine power output at all ... . And IIRC, Ethanol has about 30% LESS Energy vs a matching volume of straight gas, so you'll use more Ethanol mix fuel than you will straight gas, but 30% less energy from just 15% of the gas your engine burns isn't really going to meadn a massive drop in mpg - it'll probably be enough to be noticeable, but not necessarily anything really significant, altho that might vary with your engine's set-up & current fuel costs etc.... I know my Twin Turbo-ed & performance enhanced Hyundai really doesn't like it in any form, but the old Pathfinder 3.3litre V6 couldn't give a rats about what mix it runs - it sucks down pretty much anything from used sump oil or kero thru E10 & E85 all the way to 100 octane race gas at the same alarming rate for what's really minimal changes in its (never great ) power output, but it does it reliably for mile after hundreds of thousand miles!!

Apart from all that, Ethanol is aggressive to fuel system components and will absorb moisture from the atmosphere, which can cause rapid degradation of fuel that's stored/not used for any length of time & may also cause issues with corrosion etc in fuel systems, seals, pumps etc - altho that's more often of significant concern in engines fitted with a carburettor....

Not sure about the dates in your part of the world, but here in Oz I think it was from from 2011 that ALL petrol engined cars were required to be able to run on E10 gas, altho that doesn't necessarily remove the issues caused by leaving that E10 or 15+ gas sitting around in the tank for a few weeks or more during any period of high humidity/wet weather!

Over to you!