What kind of fuel mileage is every one getting

[GTSideSwipe]

Im getting around 10-12 mpg with the original 350 and Turbo 400 tranny with the 4.10:1 rear end.

[BCOWANWHEELS]

12 mpg with my 250 I-6 13-14 WITH MY 383 n q-jet if I drive it very easy

[Alex V.]

'85 C3500 454/TH400/4.10's, bone stock from bumper to bumper, made many an empty trip to St. Louis and back (200 mi. round-trip) at 12.25-12.5 MPG. I did it enough times to experiment with 55 vs. 60 vs. 65 MPH, with tailgate up or down, and it made less than .5 MPG difference. And the speedo on it is accurate within 1 MPH.

'67 'Burb with a .458" lift cam in an otherwise stock '79 350 (4G carb.) w/NP435, 3.73's, and 30.5" tires - I only got a scientific check on it once, which I believe was 13.8. I haven't done a proper check since swapping in a calm cam ("290HP" - .383/.401 lift, I think) but I'd estimate it improved no more than 1 MPG. Though I'm not finished tuning on it yet and the drivetrain is far from fresh.

My parents' '97 2WD 1500 Suburban (350/4l60E/3.42's, 29" meats) lays right at 2,000 RPM at 70 MPH and has pulled 20-21 MPG on long trips, laden with luggage and running the A/C. Darned if it didn't hit 400,000 miles on the un-rebuilt Vortec 350 this fall, too.

[lutronjim]

I put a LC9 with 4l65e tranny in my 70 c10. It has 3:73 rear end. 15" tires but I don't know height. Driving like grandma on back Ga roads at 60 mph it got 22.5 mpg. I had to go through three small towns but make most of the lights.

This was just over 110 miles as measured by gps - before I had speedo working. I filled up at start and end until auto cutoff.

Have measured around town but waaaay better than old 307.

[TwistedCycles]

I just figured mine up. Keeping in mind that I'm still breaking in this motor, I'm getting 12 mpg with a .030 over 350, flat top pistons, 194/1.50 heads(big chamber) .460 valve lift, edelbrock 600 cfm carb, turbo 350 trans and mid 80s power steering setup.

B.

[trac209]

Originally Posted by TwistedCycles

I just figured mine up. Keeping in mind that I'm still breaking in this motor, I'm getting 12 mpg with a .030 over 350, flat top pistons, 194/1.50 heads(big chamber) .460 valve lift, edelbrock 600 cfm carb, turbo 350 trans and mid 80s power steering setup.

B.

That's about what I get with a similar engine,my truck runs a 235/75/15 tire and has at least a 3.73 if not 4.10. Highway driving the engine is really up there in rpm. That said I've towed 2000 pounds with another 800 in the bed and it still gets the same lol. RPM is a key factor for getting good mileage. I have a Pontiac parisenne with a stock 305 qjet and plain lock up three speed auto and I can get 22 mpg highway cruising at 65-70 and I have got 23-24 if I keep it at 60 and baby it.

[cdowns]

i think the overdrive tranny with those 308's you'll find not so good // you might get 14-15mpg

[eldogg]

I've had a bunch of 73-87's with 355/700r4, 3:42, 28" tire & Q-Jets combos that would get 21-22mpg. Granted they would only get 12-16mpg around town. Maybe it helps that I'm great at tuning a carb?? Just my 2cents.

[americanmusc1e]

Originally Posted by cdowns

i think the overdrive tranny with those 308's you'll find not so good // you might get 14-15mpg

true........I have a '70 LWB with a 400hp 383, 700r4 and 3.08 rear with 30" tires.....I'm getting 10mpg

420hp usually means having an engine with a peaky power curve and they don't do well with with low gears.

[Scott Webster]

On a sunny day and not fighting the wind, I'd say I'm lucky to get 10-12 mpg on the highway. However, i'm usually playing around town and driving like I stole it. When it's low I dump more gas in. Previous owner of the engine bored it out to 355 ci., stock heads with bigger stainless valves, combo kit from Edelbrock (cam, intake, etc) Holley 750 cfm, and it's higher compression. Unless it breaks down, I'm not looking inside. Someday I'll give it a transmission it deserves, but for now it's a farmtruckish-4speed.

[mrein3]

Originally Posted by molinehotrod

I have 420 hp, 32 inch rear tire, 3.08 gears, 700r4 with 30% lower first gear and a taller over drive gear, i think it is .67. I think i am going to get 23- 25 miles per gallon.

Think is the key term above. I highly doubt you're getting 23-25 mpg.

The first thing you need to do is take your or a friend's GPS and get it receiving data. Find the screen that has mph or like on mine, "SOG" or speed over ground. Then find a 30 mph zone, get the truck going 30 mph on your speedometer, and record your GPS speed.
Then find a 45 mph zone and do the same.
Then find a 55 zone and do it again.
I bet your speedometer disagrees with your speedo by a long ways.

Once you get your speedometer corrected then figure out your mileage.

To do that is quite simple. Fill your tank full. Write down the odometer reading. Drive like you always do and fill your tank again when you need it. Write down the odometer reading and the fuel you put in.

Subtract reading 1 from reading 2. Take that difference and divide by the amount of fuel you put in the second time.

THAT is what your mpg is. Guessing by what a wrong speedometer (therefore wrong odometer) says or by counting mile markers is

When you get your speedo gears right and figure out your mileage the correct way report back.

FWIW, I get 10. My best ever is 13.4 when I still had a manual transmission and wasn't towing anything.

When I'm planning a trip where a tank full won't get me there I plan on 10 mpg.

I last filled the truck in November. I keep it off the salty roads but do plow my driveway and run it out to the fish house and back. I usually average 4-6 mpg in those conditions. I'll let you know when I fill it up this spring.

[LMN8UR]

I have broke 19 mpg with the old 350 and everyone here thought I was full of then!
Last week I dropped a new 383 (the shop says it should be 400+ HP). Hope it doesn't kill my mpg, but who cares if it's fun! I'll let ya know how it comes out.

[71meangreenc10]

These trucks werent designed to get high mileage, I get about 10-12ish around town with the 350/350 3.08's, my speedo is about five miles off........you might get 20 if everything was made of fiberglass, but again with todays light made trucks and fuel injection they are barely getting 20 and thats after 40+ years of technology and thats a 2wd auto with od......I dont mind the gas cost because there is NO car payment involved.

Smitty

[71longbed-brew]

Originally Posted by 71meangreenc10

These trucks werent designed to get high mileage, I get about 10-12ish around town with the 350/350 3.08's, my speedo is about five miles off........you might get 20 if everything was made of fiberglass, but again with todays light made trucks and fuel injection they are barely getting 20 and thats after 40+ years of technology and thats a 2wd auto with od......I dont mind the gas cost because there is NO car payment involved.

Smitty

i couldnt agree more with this statement

i'f you even remotely care about gas mileage ... you shouldn't be driving a classic truck .... i drive it for many reasons .. and MPG's isn't anywhere on the list

[1quik70]

I ran my 70 LWB with a 350/350 combo & 3.73's and normally got 15-16 on the highway. The carb was very well tuned, and the engine components worked well togther.

[northburb]

The difference between "thinking" and "reality" is all in your mind.....or math in this case.

I think I'm good looking, the reality is... I'm ugly as a picked fence....

If it turns out you are actually getting that kind of milage, please share what your secret is....

I think I get about 8-10 in my burb...( never clocked it, to affraid )

[Stocker]

mrein3, that's a great post on fuel mileage calculation. I'll add this: for greater accuracy, aside from filling up in exactly the same way every time, use the three-tank rolling average.

It's simple -- combine your three most recent tankfuls. When you fill up, add that one to your calculations and drop your oldest of the previous three. This helps minimize the inconsistencies and give you a more accurate consumption figure.

[mrein3]

Originally Posted by Stocker

It's simple -- combine your three most recent tankfuls. When you fill up, add that one to your calculations and drop your oldest of the previous three. This helps minimize the inconsistencies and give you a more accurate consumption figure.

Combining your last three or more is a good way to remove inconsistancies in how full you got your tank. If you always stop when the pump "clicks", that "Full" mark as defined by the mechanism in the handle might be different than the handle next to it.

FWIW, I just happened to fill my tanks yesterday. First time since 12/6/09. Remember my truck stays off the salt but does plow my driveway and makes numerous runs across the lake to the fish house. Fish house runs are usually 20 mintues of warm up time on the engine followed by .5 to 1.25 miles one way. Shut down. Warm up for 20 minutes or so, and run back home across the lake for .5 to 1.25 miles.

With that in mind my last tank was 3.7 miles to the gallon. Not my worst winter tank full since I bought the truck in 1994 but close.

Another thing to consider is who you get your fuel from. My daily driver gets lots of miles. 20,000 to 24,000 per year. I ALWAYS get 2-3 mpg better from the local BP station in my daily driver than I do from the local Holiday station. There are other places to purchase gas locally but Holiday and BP are my easiest places to stop at. Once you get a good baseline for your fuel mileage data, don't be afraid to try other suppliers to see if something is different.

I don't work for BP, Holiday, or any other gasoline company.

[CE20934]

The econo-boat can get 24-26 if I keep my foot out of it and loaf along at 70. However that's a TBI 305/700-R4/2.73 with 26" tires.

The truck used to get 11-13 when it had a 400 SB. Now it gets 7-9 with the 427. Same trans (SM420), same rear end (4.10), same tires (32"). I'm still tweaking the carb.

I did get 15 once with 30" tires & a 4.57 rear end. The speedo was also reading 20% high.

[mstrav1973]

another thought would be to go on a 100 mile trip with a chase car that is accurate if you dont have the gps. Go about 50 miles and then come back to the same pump at the same station. my rig is a 4x so I would think 2wd would be 13-15 when well tuned.


what do the straight 6's get with a stick?

[LONGHAIR]

Not to "pile-on", because that is not what we need here....But it is faulty thinking that getting the lowest RPM possible at highway speed will net the best fuel mileage. You really need to be in the "sweet spot" of your particular engine. For mostly highway driving and the best economy at that speed, you should probably have a cam and corresponding engine parts that work best at around 2200-2400...and the gearing to keep it there.



In case subtle hints don't work......Play Nice.

[Stano]

fuel mileage? more like fuel footage! lol not really its like average 12-13mpg est with a mild 350 400t 3.73's and 275 60's on the rear. Turnin like 3000 at 70mph

[72chevyk10]

my 4wd 454 gets 13 on the highway with 4.10s and 35's and the t350 trans. im pretty happy with that. i get about 15-16 in town

[eagleuh1]

68 C20 327 Q-jet 4 barrel w/HEI TH400 4.56 with 33 inch tires got 10 to 11 mpg driving 10 miles out and 10 back from work every day. Usually didn't go over 65 because I had to pedal to fast.

[C20-67_N_MO]

Sorry but I am calling this guy out.

Cuz myself I think he is jus trolling because there is no way he is getting this kind of mileage in a 1967-72 series pickup truck!