Very interesting topic, I just wanted to say that over here in Ecuador all we have is 89 octane fuel, I use it on my evo every time even under boost (owned the car over a year now) and my engine has not blown up/explode/broken to pieces or anything on the like. The only thing I can say is that the car does not run very spirited, if you know what I mean.
Bottom line is, japanese engineers know their stuff, they made the car so it can run safe even in low octane fuel, I know that higher octane fuel is recomended, but I don't see it anywhere being mandatory. Just my personal opinion/experience.

 

If you're running a lower octane than recommended, your car is basically running in limp mode. I'm betting that if you datalogged the car, the timing would be severely retarded and it would be way down on boost.

 

I agree with you, even though I am hitting 1.2 kg/cm2 on my stock gauge (is that the normal pressure for evos IX?) but in the end, using lower octane fuel will not brake the engine, or will it? I don't have a choice anyways

 

add OCTANE BOOSTER

 

If Mitsubishi ECUs are anything like Subaru ECUs, your car will constantly be adding timing/boost under the assumption that 91 octane or better is in the gas tank. When it senses knock, it pulls back the timing and drops the boost to protect itself. I'm not sure if this cycle can cause damage but I wouldn't put anything but 91 in the car.

 

The problem is I do not have a choice, 89 octane is the best we can get, unless I start mixing in some Avgas that I can get for the low price of 7 bucks a gallon... you are right though, because I do not hit 1.2 every time, I sometimes only hit 1.0.... I guess time will tell how long my engine or perhaps turbo will take this pulling time process

 

Avgas? Which one the 110 or 120, is it blue? You could always use Toulene or Xylene as a cheap alternative. It's what they use to boost octane anyway!

 

Yes it is blue, i believe it's the 100LL, I tried to find toluene or xylene but nobody has a clue about those over here... a little off topic question: if I can't get better fuel, can I just get a tune to run 89 octane safely and maybe even increase boost to 21psi perhaps?

 

LMAO i know this thread is hella old, but the exact same thing happend to me today lol. I leant my dad my car so i could use his truck to haul my quad around for the day. I got home and he was like " Hey I filled her up for ya son, figured id help ya out a lil" Im thinking Great saved me 40 bux. but then it hit me and i had to ask, What OCT? he says regular. Ah man sometimes parent have the best intensions.

so now im goin to fork out 50bux or so for 109 to dilute with the 87.

 

Yeah, sell your mom and keep your evo

*this is a hillarious thread*

 

Jesus H. Christ. Unless this is a 600hp car tuned on the rickety-edge, and your mom has a lead foot, the ECU will pull timing as needed. Just putting around town wouldn't hurt it, even if it was on 87. It's just not reccomended. All of this talk about octane booster, draining the tank, math equations and race gas is laughable. Just drive it around normal without going into boost.

 

:: :: you let your mom drive your evo? lol. turn down boost. DOWN... or octane booster. whatever you do stay off boost till next fill up. power

 

See I realize that the evo will be ok with the gas due to it pulling timing and me driving it nicely, cuz im on a stock map.

BUT I am so meticulous *sp* about my car id just rather put sum 100 or 109 to offset it and ease my mind lol.

 

Haha wow this thread is pretty old. Yes I let my mom drive the Evo every once in a while, don't make fun. Also, speaking from experience, just drive the car nicely (No boost ect.) until you get the empty light, then fill with 93/92 oct again.

 

When you lend the car to your mom, you should turn on the "valet mode" in your Ecu, that way, she won't be able to boost it at all...haha...Now i just got an idea, we should tell telphra to change the name of that feature to "Let parent drive mode" ;-) J/K, don't take it too serious....haha *Telphra, are you reading this?*