87 octane on 91 tune for 30k km

[ChuckTaylors27]

I figured I'd share this and see what everybody has to say bout it. As the title says, I've been putting the wrong fuel in my 2014 5.3 for a while now. My truck gets parked often for long periods and over the past 3 years, since i put the tune on, I've driven 40k km. I was putting in 91 at the start, but somewhere down the line I started putting 87 in. Today I flashed my truck to stop a code from coming up and i realized what I did. I changed it back to 87/89.

 

Thus far I haven't had any issues. Didn't even notice I was on 91. I figure I've been on 87 for about 30k km. Have I done any real damage? 

[CamGTP]

No.

 

The truck was designed to run 87 from the factory. Going to a high octane would only benefit the engine if it was making more power than stock and if timing knock was a issue at full throttle. Otherwise when we drive at 1/4 throttle for 98% of driving, the 91 octane was really just a waste of your money.

 

Tuners that say you need to run 91 octane all the time say that because that fuel will give you the most horsepower at all times under specific conditions, like going full throttle. Even if you switched back to 87 or 89 octane on a so called 91 octane tune, the computer is more than smart enough to detect engine knock if there was any and can remove ignition timing almost instantly to keep the engine running safe.

[Grumpy Bear]

This is a scenario where the knock sensor can save a motor. However there is a limit to the amount of timing it can pull. The OEM tune for 87 is less aggressive than the flash tune you put in for 91. Meaning you added timing beyond the base map and when running 87 it has to remove additional timing to get to the same place. I don't know what that limit is. Cameron likely does. He tunes.