[FRSBRZGT86FAN]

Originally Posted by mdm

Doesn't it actually pull back the engine AFTER it detects knock? In other words, there some knock must happen before the ECU adjusts the engine, so it only can prevent more knock?

Originally Posted by olsonpg

Your engine control unit adapts to the changes of octane running through the engine. I honestly have made 4000 mile road trips in the car on 87 and when i get back home i put 93/91 one back into it and its fine and over 80,000 miles of 87 into a supercharged mercedes that called for nothing but 91/93 and never had a problem.

I have heard from many engine mechanics that 87 has absolutely NO lasting negative effects on the engine besides temporary reduction of power and torque while it's in the tank.

But there are a lot of guys on here think its a cardinal sin and a slow death of the 86 to put 87 into the tank.

Would absolutely love it if some professionals in the field could clear the air when it comes to this.

Originally Posted by mdm

Isn't there a sticker inside the fulel filler door that says PREMIUM unleaded fuel only?

Originally Posted by Tcoat

There probably is one someplace yes. I only bring it up as a possible not as a given. I would hope that the ECU would prevent any issues and under normal driving it would almost be guaranteed that it would. Hard driving on the other hand could be a bit of a gamble to trust that it would all the time. They require high octane for a reason and I don't think I would want to trust the ECU to protect my engine for a prolonged period. That isn't even taking the retarded timing and resulting loss of power into the equation.

Long term there could definitely be ill effects, the IAM (ignition advance multiplier) should be at 0.7-1 on 91 or 93, it must drop well below that in order to counter the knock and sometimes that doesn't even work. It can only detect and change that when the knock occurs as well. At that point you're increasing the probability of pre-detonation because the ECU can only adjust so much after a knock occurs.