jmart69x

Is it possible to get poor gas mileage when using 93 octane for a Mustang GT that has not received a tune? I have a 2006 GT, and still have the stock airbox with no retune. When I first got the car, I was getting 18 MPG City / 21-23 Hwy on 87 octane. Then I switched to 93 octane. The MPG dipped to 12-14 City / 18 Hwy. The dealership has told me that I should not be putting in higher octane gas (unless I have a retune)in the vehicle because it is designed to run on 87 octane. I was told that the new mustangs have a Very sensitive computer. As skeptical as I was, refilled my tank with 87 octane. Almost immediately, I noticed the MPG improve to 15-17 City / 24-25 Hwy.

owero01

Thats the way it works sometime. If you are not going to get a tune, you should put a tank of 93 in it every couple of months to help keep the engine clean.

howarmat

Shell V-power does wonders!

jdback19

+1000

Drop Top 06

It also depends on your driving style... but if you're using 93 octane on a stock car, you're just wasting money... The 93 octane won't completely combust all the way since the engine is tuned for 87. It leaves tiny tiny particles.