4.10's and the auto

[SixtySix]

My car is also running 3000 RPM at 80 mph.

What size tire by chance? I don't hit 3k until around 85 or so. I'm running a big tire as well, 275/50/17 just a couple of tenths shy of 28".

 

[tlt05gt]

I am running the same size tire 275/50/17 and at 80mph I am at 3000 rpm. I am going to switch to 373 and see if it makes a difference.

 

[tlt05gt]

13.9? How fast are you going? I average 18mpg on the highway, granted you probably have more horsepower than me, but you should get better mileage than that I would think.

I drive 25 miles to work and 25 home and I get 13.9mpg at 75 to 80 MPH unless the computer is off but I dont think so because I have to fill up twice a week.
I am running a built motor (by ST Motorsports who by the way is The Best Mustang tuner in the world in my opinion) with a Kenne Bell 2.6H supercharger. The gas mileage has not changed that much from the stock motor with supercharger. With the stock motor I was running 14.1 mpg.

I have not put on the twin GT500 fuel pumps,new throttle body,new air box and down tube yet so I think it may get worse than it is. I bought the car to haul ass not for fuel economy but it does seem rather low.