I was wondering what kind of gas mileage i could expect to see if i did a 3.73 gear change in my stock 1992 mustang 5.0 with the 4 speed automatic transmission. I'm currently getting probably around 18-20 mpg Thanks!
Gear ratio definitely plays a part in fuel mileage. You'll be running at higher RPM's on the highway when you step to the 3.73. If you do a lot of highway driving, mileage may suffer slightly. In town mileage could be unaffected. How badly your fuel mileage suffers depends upon your current gear ratio and driving habits. I, personally, swapped from a 3.08 to a 3.73 in my 92 coupe years ago and noticed about a 2 mpg decrease, but I do a good bit of highway driving. Hope this helps.