Originally Posted by RJWNY
i ordered 3.92s on my 14 spot but was offered 3.21, 3.55, and 3.92 from my dealer here in NY.
Everyone says the 3.55 with the 8 speed gets better gas mileage than the 3.92 with the 8 speed, but does anyone have hard numbers? what is the real world difference in MPG?
It would really be nearly impossible to have an apples to apples comparison between the two.
Simply because no 2 people drive the same route and the same way.
Even you and I, and everyone else, your mileage varies from tank to tank just because you yourself drive differently every gas tank, sometimes may hit more stop lights, other times driving harder or passing more people.
But with a 3.92 axle ratio, you will be turning more rpms when cruising at any given speed. So if you routinely drive 70 mph on a freeway drive to work, in the 3.92's you're engine will be spinning about 200 rpms more. That uses more gas.
In city driving the difference may be smaller, it all depends on your right foot and how hard you push the go pedal.
Realistically, on average the difference may be .5-.75 miles per gallon.
And since you can have that much variance between two tanks of gas with any car, it would be hard to show it was the axle ratio causing you to get worse gas mileage. But facts are facts, if you are turning higher rpms at a given speed you'll be drinking a bit more gas.