Went to Myrtle Beach, ran 93 octane with 93 tune and averaged 15.5 on the way there, On the way back still ran 93 octane with 87 performance tune still ran same gas mileage. One thing I did notice filling up with 93 oct in SC at a racetrack gas said 444 miles to empty, But on the way back filled up at a BP and also 93 oct but read 545 miles to empty so makes me believe some stations says 93 octane but I believe it's 87 oct.

 

Miles til empty is just an estimate it's not a sure thing and the sensors damn sure cant tell the octane rating.

 

I'm not sure why this happened but I know gas stations are shady. They know what they can get away with and when the next inspection is coming. I have a local gas station here that tries to pull that stuff.

 

I don't think your truck knows what octane level is in the tank and it just estimates miles per empty based on your last tank and driving habits...

 

I agree.