So i Live in Chicago, And my 03 Evo is currently Tuned on E85, I heard during the winter its hard to start the car With E85, My question is, Is it bad if i Got a 93oct tune and Also kept my E85 tune, so i could just switch Back to it When the Weather warms up... For instance, If one week i wanted to drive on E85, And the other i just Switched to my 93 map, is that possible and is that bad on the engine? thanks!

 

You have to run out the tank to almost empty is the only problem with switching. With a proper tune there should be no reason to have any problem running e85 in sub 20* weather

 

I have an e85 tune and 93 octane tune on my evo, occasionally i switch to e85 on the weekends or for fun runs/track days. But mostly I run 93 octane for work since e85 runs out soo fast. As long as you make sure the tank is empty when you switch then you should be fine

 

Switching is perfectly fine, and having a gas tune is also a very safe idea just in case you're ever in a situation where you can't get E85.

Regarding E85 in the winter, a proper tune should have no issues starting (I'm from Minnesota originally so yes, I know what midwest winters are like).

 

Is it possible to do this with a stock ecu?

 

Yes. Search about map-switching.

 

Thanks Ill do that