When my truck was 2wd (460/C6/4.10 with 235/85R16) it got 8 mpg. Always.
I converted it to 4x4 (460/C6/NP205/4.10 with 39.5" swampers) it gets 10-11mpg. The effective gear ratio is working in my favor.

 

Like bbf835 said, effective gear ratio can make a difference. A 460 should have no problem turning big tires with 4.10 gears.

My mom's '77 Lincoln Town Car had a carbureted 460 & a C6 transmission. She kept track of her mileage and it was 10.1 mpg all-around. It was nearly 22 feet long & I'm sure it weighed at least 6,000 lb. A light on the dash would come on if you didn't use premium unleaded, though.

 

Guess I'm just gonna have to find some scales and get weighed. Like some of you, I'll have dog along, a few tools in box and one full rear tank. My front tank's fuel pump took a dump.

And really need to get her out on highway at 65 in 5th gear and then check mpg's.

Thanks everyone.

 

I get around 10 mpg. 460/ZF5/BW1356/4.10 with 35" BFGs. I should know the weight since I dropped off some scrap metal yesterday, but I've already forgotten. Maybe 5500? Or was it 6500....?


I use my truck to haul mulch quite a bit, I'd be interested to see what it weighs with the bed filled. I can't tell a difference in acceleration when it's loaded down, but the handling sure does improve.

 

Our 89 F350 4x2 Dually with 460 and 5 speed usually gets between 9-10 mpg while towing our racecar.

 

rss, I'm envious. I haul only tool box and 20 lb dog.....and get 8 mpg