If one puts 87 octane in, does one just retard timing under boost or does one have to reduce cruise timing as well? Granted a tank of 87 is only 3-4 dollars cheaper, I am curious.

 

lowering timing will help but you may also need to lower boost and not drive it like a wild man

 

Like Mellon said, just lower the boost.

Too much timing is bad for any octane. At least with low octane the system automaticallly retards from knock. At high octane and too much timing there is no knock, but cyl head temps increase to eng part melting points

 

Why not just sell the Evo? I know I'm being negative here but when you're saving 3 dollars per tank on a car like the evo, you will be better off with something with 2x or even 3x mpg

 

I was just wondering for my own knowledge. I already admitted the price difference is miniscule. If I was worried about the price, I could sell the evo and probably get a brand new civic.

 

If you're worried about MPG's, you can always create another rom with leaner AFR's and higher timing in cruise area's. That's what I did and I get around 370 miles on a tank of 93 with occasionally feeling a little foot slamming happy on my 2g eclipse. I run about 35-37* during cruise with 15.3 AFR.