So long story short I have been assembly a shell and stupidly enough forgot to drain the 2+ year old gas. Speaking to the previous owner I found the fuel to also be E85 (current engine is stock). Obviously the engine is running horrible (misfiring on all cylinders) but does run and idle. The car has ran for maybe 15 minutes all together on multiple occasions. Obviously I am going to siphon out the E85 and add 93 with some octane booster but is there any permanent damage that could have been caused or things I need to look for?

 

As long as you haven't driven it under moderate/high load, you should be ok.

 

E85 has higher octane than gas, however it also contains less energy, which requires larger injectors. Essentially with a stock tune and e85 amounts to running ultra lean.

 

You should keep an eye on the fuel line connections since e85 could cause any rubber seals to deteriorate.

 

No need, they'll be fine. I've played with E85 extensively and never seen deterioration issues on modern cars with OE parts.

 

why would e85 cause rubber to deteriorate, as opposed to gasoline?