I had no intentions on being hostile or offending you. I just think you'd be better off just running premium gasoline as opposed to spending the money, time, and effort it would take to properly use lower-grade gasoline. That's all. I apologize if I offended you.

 

I hope you got a knock lite....it is going to kncok and then throw a rod if you get on it and boost.

 

When the people say its knock resistant they mean that the higher the octane the slower the gas burns and the higher the temp it burns at. The reason higher compression engines and forced induction engines suggest the use of 91+ is because under the increased pressure(or heat from the compression) in the combustion chamber the gas may combust prematurely.
As many have said I would not recommend using a lower grade gas in your car, however I will recommend getting your car tuned. I tuned my car and since they run rich from the factory I was able to lean it out quite a bit (make sure you are using a Wide Band 02 sensor). Since my tune I have noticed better gas mileage during cruising and overall better average mpg. On average I get 24-27mpg, on long drives I get around 34 mpg. My mods are Walbro 255, Apexi intake, Hks Hi-power turbo back, test pipe, ets intercooler and pipes, 23lbs boost on a self tune.

 

When they engineered the Evo, Mitsubishi knew that anyone, whether they be genius or fool, if they happened to have or could obtain use of the necessary money, could end up driving an Evo. They also knew that any possible button on the gas pump could and probably would be pushed when it came to refueling time. So, they installed systems that would protect the engine when the optimal fuel wasn't used, systems that pulled timing and reduced boost.

Even if you go to the pump and press the 94 octane button every time, how do you know that that is what you are getting. So, the stock Evo was built to protect itself from bad fuel. Now, if you have done modifications that have removed some of those protections – well, that is your problem.

 

I would not do it, I had a friend that filled his car up with it. He had mods and tune you name it, he blew 2 coil pack cause of it.

 

My mom put 87 in the Evo and my 1.8T VW Jetta. Both threw Catalytic Converter Efficiency Codes. After going through the tank and maybe a take of 93 the code cleared itself. Not good for the cat.

 

I love it, keep it going, lets see whats next.

 

My guess is the ecu threw a ton of fuel in the mix to combat knock.

I am going to post this one more time and this thread is done:

If you retune the car for the octane of fuel being used, EVEN 87, it will be fine. This is not something that should be done on a stock or 93 octane tune. That said, IT CAN BE DONE without hurting the car.