MPG comparison...How's yours?

[dieseldude4bt]

I mostly just use it for overdrive but when you are towing it is nice to be able to split gears.
I have had it for 16+ years and it was used when I got it so they hold up well.

[66customcamper]

Haven't checked for quite a while but was around 10 mpg with 327/4bbl/sm420/
4.56 gears/7.5x16 bias plys running empty. With about 3000 lbs of firewood, I think it was around 7 or 8

[AcampoDave]

Originally Posted by steveb64

I'm at 9 mpg city, 9 mpg highway, 9 mpg all the time.
Mild+ Cadillac 500, TH400, Holley 870, 3.73 factory limited slip, 28" tires, lots of torque, big right foot.

That's the funny thing about those motors. I got one still in a Cad and its 11 all the time. I like to tell people it uses five gallons an hour, no matter where I go or what I do.

[steveb64]

Originally Posted by AcampoDave

That's the funny thing about those motors. I got one still in a Cad and its 11 all the time. I like to tell people it uses five gallons an hour, no matter where I go or what I do.

I need to recheck mine, I may be up to 11 now.

Turns out I had a crack inside my th400 case since assembly and install. Burned clutches and all, may have been experiencing slippage.

[T Herder]

65 GMC K1500 305E V6 with a Mallory Maglite distributor, 1988 GM Throttle Body Injection, SM420 with a married Gear Vendors OD, divorced NP 205 transfer case, 4.56 final drive gears, BFG All Terrain 35's, plus a few other things.
I regularly tow a custom Sundowner 4 horse trailer with a GCVW of 18,000 lb. Log book verification shows the best mileage empty has been 18.61 MPG, worst, 7.2 MPG has been with a max load and pulling 21% grades in 4WD.
Average towing mileage runs 12.5-14 MPG, non-towing with a light load has been 14.8-16.4.
Best regards,
T Herder

[ChrisDollins]

Our 66 got over 15mpg on the hwy. Not sure what it gets mixed driving. Factory rebuild 250 with a hei. 3 speed and 28" tires. Was really suprised with old truck, didn't expect it to get that. Ready to get an overdrive in it and check it again.

Chris