If I was to use the 4.10's would that hurt my everyday gas mileage or does that depend on my motor and programming. In the process of building engine just trying to get some professional information.

 

During my daily commute I never used 6th and seldom 5th. So when I put the 3:73's in I found that I just used 5th more. So mileage didn't realy change except that I was puttting my foot in it more.
With and automatic I'm sure it would make some difference.

 

Depends on if you are an auto or stick. Auto, yes. Stick, not so much.