Rusty_S85 Posted July 13, 2021 Share Posted July 13, 2021 I owe the mileage to the 5spd trans and 3.08 rear diff. I'm running wide 275/60-15 tires, but they're the exact same OD as the stock sized 215/75-15 tires. My speedometer is very accurate, so that makes my calculations even easier. I usually double check the actual distance driven, but it's always the same anyway. I had hoped to hit 20mpg with the truck after it was all broken in (10k+ miles on it now), and I'm sure I could do it...and likely even better with the EFI. In 5th gear, 70mph is only 2000 RPM. That is just at the beginning of my power band. It's still a bit sluggish at even 1800 RPM, but at 2000 RPM is just winding up and I can climb hills with it like that. I have to be careful not to speed with it... Yep 5 spd with a 3.08 will help for economy long as you dont lug the engine down too much. Im looking at going 3.25:1 axle ratio but may have to run 3.00:1 if the C6 im going to have built has too much slippage. Im banking on 3-5% slip so I can run 3.25:1 axle ratio which would put me at 2.96:1 I think it is after accounting for the taller than stock 31x10.50-15 tires. This should in theory put me between 2,400 - 3,000 rpm for 65 - 75 mph. But in your case if your engine isnt lugging too much at those rpm then I say go for it cause it will help your economy. Ideally I want 20 mpg highway but realistically I dont know if I could get 20 mpg but maybe I will be surprised after I get everything to where I want it. Link to comment Share on other sites More sharing options...
Recommended Posts