FNG intro

[seagreen12]

I am SG12 doing my intro post:
I do freelance commercial diving (not lately) and work overseas supporting the GWOT as a counter IED Subject Matter Expert I have had an interest in 6.2NA diesels for a while and gearing up for a demo job that I am going to be supporting where I need a truck.
I found an 86 (I think) former mil chevy 1 ton truck with a 6.2 the guy thats selling it is never around and i have left a couple of messages. I am looking for general rule of thumb milage answers (I know I know)

I have had several diesel vehicles including an M37 with a herc diesel that got 19-20 mpg geared real low, a Suzuki Samurai that i put a volkswagen diesel in it worked great but I broke the frame! and drowned the motor throwing a rod after about of year of service.

I am presently driving a 76 240D 4 speed that gets an unbeleivable 40MPG sometimes even better! which I traded a 22 pistol for!

Anyway just an intro and looking for rough estimate ideas of MPG for the MIL 1 ton chevys.
Looks like a good forum and I look forward to reading and learning from the experts.
SG12
sends

[Robyn]

Well for whatever its worth my 95 3500 dually 4x4 crew cab with the 6.5 will do 19 Hwy and 15 city

A similar truck with 4.10 gears and the 6.2 should be in the neighborhood somewhere.

A lot depends on the condition of the engine, injection pump and the injectors.

Robyn

[More Power]

Some of the retired military 6.2 trucks were geared lower than 4.10, while most were 4.10 geared, so it would be helpful to know what the gearing might be. A 4.10 geared truck without an overdrive transmission makes it a pain to use on the highway at today's freeway speeds. 3000-rpm at 70 is not a lot of fun.

Cruising engine rpm is a big factor in fuel economy. The 6.2L diesel has a best BMSFC (Brake Mean Specific Fuel Consumption) rating in the 1800-2000 rpm range, which means best fuel economy comes when operated in that RPM range. You'll want (simply must have) an overdrive transmission... Without an overdrive, you'll likely see mid teens mpg at 60-mph. An OD will give you 4-5 mpg, and you can drive somewhat faster - with less noise. ;)

Jim

[ccatlett1984]

ALL CUCV TRUCKS HAVE 4.56:1 gears, unless they have been swapped out.
Also ALL CUCV's (Trucks & Blazers) got the TH400 trans (NO 700R4's)