Re: Fuel efficiency...what MPG do you get?
 

I had an 83 short bed with a 355 vortec head engine, 700r4 tranny, and a 12 bolt with 3.08 gear with 275/60/15 tires and got 22 most of the time on the interstate. I pulled a full trailer with an 88 camaro on it and still got 17 going from birmingham to ft. walton beach.

Re: Fuel efficiency...what MPG do you get?
 

I have a stock 305 tbi with a 700r4 and 2.73 gears. As long as I keep out of overdrive, I can get 17-18 mpg. I drive back and forth to work averaging 55 mph.

Re: Fuel efficiency...what MPG do you get?
 

Haha, I have a '78 K20, 350/400/np203 and I'm pretty sure 3:73's getting about 6.5 mpg. not sure the actual mileage, but thats what it feels like

Re: Fuel efficiency...what MPG do you get?
 

78 c10
76 400
373 rear
th400
I get smiles per gallon

Re: Fuel efficiency...what MPG do you get?
 

78 K10. Nice weather and hubs unlocked I get 10 in town and 12 on the highway.

Re: Fuel efficiency...what MPG do you get?
 

1974 Chevrolet K20.
350 has head work consisting of a valve job, port and polish both sides,matching intake, stock cast intake, and a 600 edelbrock mechanical secondaries. Has full length flowtech headers into a 2.5" straight true duels exhaust.
SM465... WITH 4.10's and 39.5" Baja belted atz's I get 18 highway mpg at 75. 18 at 55 as well. Now it get 1 tank to about a year as the rear end is out lol.

Re: Fuel efficiency...what MPG do you get?
 

'83 K30, warmed-up 350 (cam, headers, AL intake, modified Qjet, stock heads and compression) , 4.56 gears, 205,SM465, 305/75/R-16 on 16x10 Alcoas = 12 mpg/HiWay with a ton in the bed.
'90 stock V3500 3+3, 454 tbi, 4.10's, th400 = 8 to 9 mpg combined. (55 only on the interstate or the gas gauge moves much faster)

For a comparison ; stock '9x something G20 van, 6.2 NA diesel, 3.08 gears and a 4L60 = 18 mpg combined. Fully loaded all the time.

edit; almost forgot. 2000 3500HD, TD 6.5 , NV 4500, 4.63 gears , 10,200lbs - bed empty/toolboxes full, 15 mpg combined/mostly city - with one hour drive @ 55. Checked two tanks with about the same driving 15 mpg both times, 10 mpg if you don't short-shift the gears and just let it windup like a gas engine.

Re: Fuel efficiency...what MPG do you get?
 

I should have given more data:

78 K10. Nice weather and hubs unlocked I get 10 in town and 12 on the highway.

350, 12-300-4 cam, Edelbrock 1406 on dual-plane air-gap manifold, Hooker headers, H-pipe, TH350, 3.73:1 on BFG 31" tires.

Re: Fuel efficiency...what MPG do you get?
 

86 c20 with 260hp crate with 63k on it with one bad ticking lifter and one burnt vavle sm 465 3.42 gears with stock q jet 14 where i live with my heavy right foot. 21-23 down the highway depending on ebrake draging or how flat the highway is. at 75 i get 16-17 all the time. truck rolls around at 5600 with me in it plus the tools i have in it at all times. i dont know why but she does good on fuel even my k30 got me 18 at 60 with 6.2 and 4.10 and the c30 i have is 10 with 454 465 and 4.10. all my trucks are stock drive trains only thing i have done to the 86 is turn the timing up and tune the carb once in the 8 years i have had it and it is the origanal to the truck as far as i know.

Re: Fuel efficiency...what MPG do you get?
 

1973 C20, 350 engine with a little headwork, Comp Cams 252H, Edelbrock Performer intake manifold, Edelbrock 750cfm carb (too big), non-air manifolds, full exhaust - it's a truck engine, but a lot better than stock. TH350, 4.11s, 245/70-17 tires, tow mirrors, utility bed.

I tend to see around 10. Hoping to increase that by at least 50% with a 4.8 or 5.3 swap backed by a 4L80E... I think the engine spinning pretty fast really hurts freeway mileage, so overdrive should help a lot.

Re: Fuel efficiency...what MPG do you get?
 

Surprised no one has jumped in with their diesel mileage.

Re: Fuel efficiency...what MPG do you get?
 

Glad someone brought this thread back to life. I was wondering what the stock engines were getting. Thanks

Re: Fuel efficiency...what MPG do you get?
 

See my post up 4 from you. Have two diesels listed.

Re: Fuel efficiency...what MPG do you get?
 

23mpg. See my sig. 1/3 country, 1/3 highway, 1/3 city. Fully loaded 87 R10 , 6.2 diesel, 7900R4, 3.08's, stock size tires.

Re: Fuel efficiency...what MPG do you get?
 

I have an 84 K20, 350, quad with a 465 trans and 3.08 gears. IF I keep my foot out of it I can get 17 to 18 MPG pulling a 7000 pound trailer on the highway. Around town I get about 10 or so. Truck is all stock right down to tire size. I think the tires are 185-75-R16 and I run them at full pressure of 85 PSI.

Re: Fuel efficiency...what MPG do you get?
 

84' C10
TBI 305 swap
TH350 w/ 2200 stall (really about 2400 in the truck)
3.08 gears

I drive it like I stole it. Last tank was about 9.6 MPG. Used to get about 11-12 when I had the 700R4.

Re: Fuel efficiency...what MPG do you get?
 

74 k5 in sig when it was an auto would average 15 highway and about 11-12 city trans didnt like driving slow niether did I :lol: so it stayed out of town for the most part all while pushing 33x12.5s on a 2.5 inch lift. Havent driven it enough as a stick to know if it got better or worse:devil:

Re: Fuel efficiency...what MPG do you get?
 

I have almost the same setup. 383 stroker, 3.73 gears 700R4 tranny (we just put in the lock up converter, it was without the lock up feature until now), 28" tires, dual exhaust, 650 CFM carb. Prior to adding the Lock up converter, I averaged 15 MPG on long trips.

I agree, with the idea of a LS series engine and a T56 tranny. Good horsepower and a lot of room to adjust.

Re: Fuel efficiency...what MPG do you get?
 

No speedo 83 6cyl 465 4 speed tall gears guessing good but man is it slow.
Guys lie about gas milage worse than they lie about you name it?i had an 02 gmc HD with 8.1 gas allison on interstate cruz at 65mph never got 12 had a 99 with the 5.3 got 16 and thats the best milage i ever got in a pickup.

Re: Fuel efficiency...what MPG do you get?
 

84 c10
350 700r4
about 11 mph in town
on a good day.

Re: Fuel efficiency...what MPG do you get?
 

The 84 I had a 305,350 trans,2:73 gears got 10-12 on the highway. I could watch the gas hand drop. SERIOUSLY. I think it was supposed to have a lockup converter on it but don't know for sure. But I don't have to worry about it any more the exwife got it and the 72 in my avatar in the divorce. Oh well it happens,,,,,,,

Re: Fuel efficiency...what MPG do you get?
 

81 c10 lwb old 305 new th350 no idea on gears and 75% of driving on highway at 55-65 mph

averaging about 12. i know its running rich and needs a tune up but since it fires up at 23 degrees with no choke im not touching it right now.

Re: Fuel efficiency...what MPG do you get?
 

'85 SWB C1500, 355 sbc, 3.73 axle ratio, TH700R4, 28" tires, Quadrajet


14.5 MPG, 25 miles round trip to and from work.

Re: Fuel efficiency...what MPG do you get?
 

i think there are alot of facters that need to be made in this. like driving habbits tire pressure timing and carb tune. i mean my 78 monte got 12 with a all stock 305 after some tuning and tune up and and turning the timing up some(6 to 12) it jumped to 18 on the highway. lot better then the 12. with the 350 and better pipes and no cat and tuning it leaner i can get 24 with ac on. but i like power and to go faster down the road so i get 20 most the time. also its all about rpm's and power. too high lots of fuel to low lots of fuel. need the sweet spot

Re: Fuel efficiency...what MPG do you get?
 

I agree but I try to keep tires at correct pressure, I ,ve tried timing all over and ran speed limit or A little over by 5mph. Still around 10-12 mpg. No lead foot when figured. The 72 was the same way but I expected it with it.