Ok so i know mistu recommends 87 only. I recently ran my tank down to empty, then filled it with 91. I ran that for a couple weeks, and now my tank is back to full at 87. I honestly can tell a difference in performance, but the real kicker is the difference in MPG. Due to the performance and MPG gain using 91, im strongly considering switching to 91 full time. My question is; am I hurting my engine if I do this? Will the fuel burn too hot for my gaskets, seals and seats? Thanks for any advice or info!

 

no not at all. you can run 91 perfectly fine. except im not sure sure but I think they have added a 10% eth. mixture, but you should definately be ok running 91 full time.

 

you should be fine. I ran 91 on my lancer for 2 years before I got my evo and it was fine

 

I did notice my temp meter registered a lil warmer when i ran 91, so thats where my concern came from. Thanks for the info

 

I run 91 all the time...not only is it a high octane, which doesn't really mean much for our cars, but the fuel is cleaner than a regular 87.

 

It is fine. U will gain a little bit of extra torque too.

 

the higher the octane the cooler it will burn and more resistant it is to knock meaning ignition temps are higher and it burns slower.