Can a C3500 5.7L 4.10 beat 10 MPG?

[89GMCJOHN]

(quote) For a Regular Cab Long Bed with an L31 5.7L and a 4.10, I'm assuming that this is normal and there's not much that I can do to improve it, short of changing the rear end gear ratio, correct? One of these days I'll get the fuel pump / sending unit replaced and go back to watching the fuel gauge instead of paying so much attention to the actual MPG...[/QUOTE]

RCSB ,Carbd 360, 10:1 ,3.08, ramjet mild cam ,1.6 rockers, s10 converter ...right at 10-11 mpg... all in town driving.

 

[lxe4]

mines 96 k2500 5.7 auto with 3.73. I got 10 in town for years. It was closer to 12 until I got some new tires that where noticeably heavier than the old worn out ones. Many years later I bought a good size camper and couldn't do over about 90 with a tailwind on the prairie bringing it home and used god knows how much fuel. I could feel it take away power after about half throttle so some kind of limp mode. I had the O2 sensor code on for all those years. They dont give those ****** things away but wow, I got soem new ones and started getting 12-14mpg in town and 15-17 on the highway depending on the weather. With the trailer it doesn't even do that bad. Still 12-13 or better if I go about 100.

 

[alpinecrick]

For a Regular Cab Long Bed with an L31 5.7L and a 4.10, I'm assuming that this is normal and there's not much that I can do to improve it, short of changing the rear end gear ratio, correct? One of these days I'll get the fuel pump / sending unit replaced and go back to watching the fuel gauge instead of paying so much attention to the actual MPG...

Doubtfull changing the gear ratio will help the MPG. Waaay back when......I had a 75 SWB K10 with a 350, TH350 and 4.10 gears, and, a 76 SWB K10 with a factory 400 SB, TH350 and 3.73 gears. The 75 got 15 MPG empty, the 76 got 10 MPG.........

 

[Supercharged111]

Yeah the gears IMO don't seem to make that huge of a difference. Especially mixed.

 

[Duncan Bramlett]

My Burban is a 96 with the 454 and 4.10 I get 13 around town and 15 on the highway consistently, but I drive very conservative also.

 

[DerekTheGreat]

My '89 K1500 regular cab, shortbox 350 five speed with it's 3.73's has been consistently doing 15.6- 15.9mpg the past four fill-ups. It's been a mix of 85% freeway and 15% stop & go. I try to do no more than 70mph on the expressway and am pretty easy on the go-go juice pedal. I'm usually shifting before 2k RPM too. I also try to keep the throttle position constant, no sudden movements and incorporate lots of engine braking. But I find myself nailing it 2-4 times per tank. Confident I could break into high 16's if it was all freeway. Even better if I did 60. Truck is bone stock.

We once had an '88 C3500, regular cab long box 454 TBI with a SM465 and 4.10's. We did no more than 60mph as it was really winging RPM wise and managed 7 to 7.5mpg no matter what we did with it. Truck was also bone stock. I like them that way.

 

[JCribb]

I have a 94 TBI 350 (.040 over) vortec heads RV cam, headers, all tbi mods, headers, free flowing exhaust, new computer prom, 4.10’s, NV4500, 4x4 SF14 bolt rear.

I consistently get between 13-16 mpg. Towing I get 11-12 mpg.

 

[Tom P]

Had a 2000 K3500 w/ 7.4L 4.10 dually. On a good day driving down hill with a tail wind, I got around 11.5-12 mpg. Towing my 6500lb travel trailer I got around 9. Mileage usually has more to do with how you drive it and how its maintained rather than what its equipped with. My 2010 GMC 2500HD 6.0L gets around 18 highway, 12 city and 10 avg towing our 7500lb 5th wheel. I don't push it hard, but I don't baby it either.

 

[Spookers]

It's the tbi holding you back.
I had a 305tbi w/ 4l60e, 3.08 and got 10mpg if you were easy on it or hard on it.
Swapped in 3.73 (about this time I got another daily so thought what the heck) still got 10mpg.
Strapped on a supercharger and crammed about 7psi into the tired engine, still 10mpg.

Puked the motor and swapped in a stock 305 out of an 86 caprice with 400000 on the clock and instantly got 17mpg with my foot to the rug most of the time.
Though that's without towing a trailer but had a pair of 3 wheelers in the box from time to time and that didn't seem to change the mpg.

I'd assume by swapping to a carb you should be able to get 15mpg unloaded and around 10-12mpg loaded

 

[GingerRage]

When my (now project) 1994 Sierra 5.7 was runnin' I could baby it or romp on it and still get 11-12 mpg. It didn't matter if I were in stop & go traffic or running 100 on I75. Very, very confusing to me, I never could wrap my head around it.

Come to think of it, I replaced the motor with the same model year and everything and nothing changed in terms of MPG's.


I can't wait to get the truck done, it'll be worth talking about on here. The poor girl's been sitting in my garage since mid-late 2014.