What would a 6.0 get for gas mileage mated to a t-56 running 4.10 gears with 205/75/R15 tires? Vechicle weighs about 3k.

 

With a vehicle that light I don't see why it couldn't get above 25mpg on the highway. That 6th gear rocks for fuel mileage on just cruising around.

 

Will also depend upon the following factors:

1.) Aerodynamics. Low drag vehicles will get better mileage. Put it in something with the aerodynamics of a barn (like say a van) and it'll do much worse.

2.) Transmission ratios. The T56 does have different ratios available. I think all of the LS1 type use the same ratios, but don't remember for certain. I know the LT1 cars had different ratios around. Not necessarily a big difference, but....

3.) Driving style. Your driving style and driving conditions (highway at steady 65 or highway at 75 in heavy traffic, weaving in and out, lots of throttle and brake) play a suprising role.

4.) Engine modifications. Some engine mods will help it get better economy (like free flowing intake and exhaust). Some tuning may make economy better, some may make it worse. Cam & head work are likely to make it worse.

5.) Vehicle drag. If you're running 4wd or Awd, expect to pay a penalty in additional driveline drag. I don't expect you're in that boat, since making a T56 work with 4wd is extremely difficult, but figured I'd mention it.

I think XLR8NSS's estimate of 25mpg + is reasonable. In a vehicle with a good aero package, and only 3000lbs, driven reasonably, it may average 30 mpg or better. Go the other way, and you may struggle to get 15.

'Dreamin'

 

Thanks for the input.

 

Holy chit that's a big picture in your sig

 

PM has been sent.

 

My Corvette is around 3200 lbs. I am running a tire a little shorter than you mentioned and with a 3.42 gear ratio. If I drive decent on the Interstate I can get 30 to 32 MPG (something that doesn't happen much). My truck is 4300 lbs. with 4.56 gears and a 29.7 tire, running between 85 and 90 I got 19.888 mpg on a trip. Maybe some of this will help

 

That thing would get some killer 60's with slicks and a good 6000rpm clutch dump.