I have been researching for a long time and cannot find a suitable answer. I really need some expertise. I have a 1996 JDM EVO IV and I am wondering what fuel I should be using. I know the car is tuned in Japan for 100+ RON which is equivalent to ~95 here I think. The problem is that in Canada all I can get is 91 or 94. Here is the question:

Our 94 is up to 15% ethanol which I have always been told is very bad for older cars. Also, that Japanese domestic cars are not meant to run ethanol. Will running 94 with 10--15% ethanol cause any ill effects (damage seals, etc)?

I have been using 91 octane without ethanol (still has up to 5% here because our gas sucks) for like 2 months. I learned that this is in fact very dangerous and will greatly increase the risk of detonation. Is it unsafe for me to run 91 octane fuel (keeping in mind I don't WOT or boost all over town)?

Then I had the idea to try using the 91 and adding an octane booster. But I realized this would only add a couple tenths to the octane which isn't enough.

I know some of you might suggest a tune on my fuel of choice. But keep in mind that the IV can't be reflashed and that I don't really have the money to justify spending $2000+ on an aftermarket EMS currently.

What do you think is the best course of action?

Thank you

 

Install an evo 5/6 ECU and then get a tune.

 

I was considering this as well. But I've heard that the EVO 5/6 already have a lot of problems with not reflashing properly. And that it's even worse on a 4 with a swap. Any experience with this?

 

No issues with flashing my 5. I'm on SD with it too.

 

Good to know. How many times have you reflashed? I've heard you can get locked out after multiple reflashing attempts. And what program did you use to flash?

 

Over a hundred times with Ecuflash

 

Thank you. I will definitely look into swapping a EVO 6 ECU and using Tactrix+ECUFlash.

 

This still leaves one thing unanswered. Even if I do tune using our fuel should I avoid the 94 octane ethanol blend? Added knock resistance would be nice but I'm not sure about running it in an older JDM car.

 

Its basically the same engine as an 8, so if its good enough for an 8, its good enough for yours.

 

It's perfectly fine for the engine (good even) but what concerns me is the fueling system. Fuel lines and seals in older cars are not designed to use ethanol, it wrecks them.

 

A 5/6 ECU and can be had for less than half of what you think. I have a PowerFC if you are interested.

 

Your thinking too much... yes you would be correct if you were running E85 all the time and that was it. Ethanol blends have been part of the US car/gasoline availability for 30yrs +..hence the summer/winter blends. If the evo was 60's or 70's vintage--and yes I know they didnt exist then, you might have some but very little concern. Your fine-- just get it tuned.

 

I ended up getting an EVO 6 ECU for $200 and I will be installing it soon. I will get a tune as soon as I pull the car out of storage this Spring.

 

I realize this whole thing is being overthought. Thanks for your input. I will be getting a tune on 94 this Spring.

 

The ethanol is just used to bring the octane level up. I have 1998 evo 5 but with 8 motor. I run e50 pretty much 90% of time. I buy raw ethanol and mix 50/50 with 95. Im still on standard fuel lines but have better fuel pump more suitable for ethanol. About to retune and go e85 but will upgrade all fuel lines. As for ecu I have 2 evo 5 ecus. 1 for 95 and 1 for e50. Many reflashes and no issues. You can run one and have two tunes if you add an extra pin and have it switched for tune swap