Question. Would the car run if you mixed in a gallon of E85 with a full tank of 91?

 

your car would blow up and rip a hole in the space time continuum destroying all existence on earth.

 

Will probably lean it out some...

 

You would probably have to tune for it..

 

that happened to me once. i divided by zero.

FML

 

Yes it will run.

What the effects will be depends on a few things. Is the 91 octane 10% ethanol or 100% gasoline? If the 91 octane is 100% gasoline you will be about 93% gasoline and 7% ethanol. This is perfectly fine, since most gas stations in the US use 10% ethanol in their gasoline.

If the gasoline is 10% ethanol, this would make the fuel mixture 16% ethanol and 84% gasoline. This isn't going to hurt the car, but you will more than likely run slightly lean. It should raise your octane to about 93 - 94.

 

My friend did this in his sti. Put in a gallon of E since he was seeing a degree of knock in some places. Instead of tuning it out he just put some E85 in with the 91 lol. It actually got rid of the KR, but he doesnt have a wideband so i dont know what his AFR was.