Gas Mileage?

[dmw319]

I know a 67-72 chevy is going to be a hog on gas. I'm cool with that. I'm picking up a 1970 c10 stepside short bed (350/auto/stock rear end 3.42s i think?) next week in Indiana and driving it home to NC and am curious what she will get, highway and city.

SO, what do you guys get as far as gas mileage in your trucks?

Details to give: Auto/Manual, Bed Size/type, Engine, gearing, etc.

[Dunenutt]

My longbed got 10 when it was 2wd. Fairly stock motor .030 over, AFB, TH400, probably the same gears.

Now 4x4, 3.73 gears, TH400, .060 over, gets a solid 8 MPG! Bathroom breaks, are a non issue

[dmw319]

phew. big change from my wifes MINI at 35 mpg average!! I guess we even eachother out

Oh and I forgot mine is 2WD, the 350, stock motor as far as i know

[jocko]

i would say you can expect between 10-14 mpg depending on driving habits and rear gear ratio. Probably the best bang for the buck upgrade you can do is to install an overdrive transmission like a 700R4 - a pretty simple swap since you already have a th350. Search this site for 700R4 and you'll find plenty of articles. That will give you better bottom end performance also because of the higher numerical gear for 1st in a 700 vs the 350. Around town you won't see much of a difference in mileage, but on the highway, the 700 will improve it quite a bit. If you won't see much highway time, probably not worth the swap, but if long trips may be in your future, I'd consider one. Might get you up into the high teen for highway mpg.

[dmw319]

Thanks Jocko!

I don't do much highway driving, but every now and then I drive to my folks lake house that is about an hour away so it might be worth it. Maybe if I find a 700 for the right price one day when I've got some time for the swap I would consider it. 10-14 is about what I was expecting.

[jocko]

Originally Posted by dmw319

Thanks Jocko!

I don't do much highway driving, but every now and then I drive to my folks lake house that is about an hour away so it might be worth it. Maybe if I find a 700 for the right price one day when I've got some time for the swap I would consider it. 10-14 is about what I was expecting.

If just an occasional 1 hr trip, it would probably take about 900 years to recoup the cost of the 700R4 in mileage savings - so I'd drive it as is and enjoy it. cc69rat outlined the nuts and bolts of the $ picture - it really is a tradeoff like he mentioned - the point being, and I agree with it, even with below average mileage by today's standards, it is probably still equally or even less expensive to OWN and operate an oldie but a goodie. If you look at it that way - the cool factor is essentially free!

[CC69Rat]

Old truck
8 mpg - $400 month gas bill - super cool and makes you happy. No payment. Appreciates monthly, things you add to it make it worth more for the most part. Safe, solid.

New (anything really) 35mpg avg - Gas bill 25% of the truck, BUT ~$500/mo. car payment. + $100 mo. in depreciation, $100 month in intrest. Keep it two years, you're luck to break even. Coolness factor goes way down. You get in any type of accident, you and your family are in more danger of being hurt.


My point being, yes these trucks are gas hogs but apples to apples it doesn't really hurt as bad as it seems. My old GMC gets 22mpg or so. Stock 350, 3OTT. SWB, stock gearing. (feels like 3:55 maybe, non posi. SWB truck, drive like a grandpa and tractor it around a little bit. No high RPM, or twisting it up any at all)

I could buy a new truck and get 22mpg. .. but why? Loose my butt in depreciation ?

My Big Block truck, that will be different absolutely but I don't drive it every day.

I'll keep my wife in the new model car, leather, air conditioning, etc. I'm good with my trucks and put $500 mo into them instead of the payment. Just my .02.

[Dean'smeanmachine]

Originally Posted by CC69Rat

Old truck
8 mpg - $400 month gas bill - super cool and makes you happy. No payment. Appreciates monthly, things you add to it make it worth more for the most part. Safe, solid.

New (anything really) 35mpg avg - Gas bill 25% of the truck, BUT ~$500/mo. car payment. + $100 mo. in depreciation, $100 month in intrest. Keep it two years, you're luck to break even. Coolness factor goes way down. You get in any type of accident, you and your family are in more danger of being hurt.


My point being, yes these trucks are gas hogs but apples to apples it doesn't really hurt as bad as it seems. My old GMC gets 22mpg or so. Stock 350, 3OTT. SWB, stock gearing. (feels like 3:55 maybe, non posi. SWB truck, drive like a grandpa and tractor it around a little bit. No high RPM, or twisting it up any at all)

I could buy a new truck and get 22mpg. .. but why? Loose my butt in depreciation ?

My Big Block truck, that will be different absolutely but I don't drive it every day.

I'll keep my wife in the new model car, leather, air conditioning, etc. I'm good with my trucks and put $500 mo into them instead of the payment. Just my .02.

that was the best comment ive ever read. you ROCK

[70STOVEBOLT]

I average 13-14 with my 70 2wd swb 250/TH400 3.73 but I don't drive it on the highway, only about 20-25 miles a day back and forth to work or running to the store for something.
Wife has 04 GMC Envoy 4X4 w/4.2 and overdrive, it averages 16, but again, not really any long trips. So like CC69Rat said, the coolness factor is much higher in the 70.

[70STOVEBOLT]

To add to CC69Rat's comments, my plates cost $41.75 every year and insurance is approximately $20/month. Granted, that is PL/PD but it ain't no show truck!

[ricks71pu]

New rebuild, .30 over, headers,454, 1971 GMC LONGHORN SIERRA GRANDE, 6-8 m.p.g.
drive it everyday, what a fool, huh? I LOVE IT!!!!

[ryanmctee]

Funny CC69Rat, I just bought my wife a new-used beautiful 2002 Lexus. Leather, Air, GPS, all the crap I don't want nor need. But she's happy as all get-out. I'll keep working on my truck and have something EVERYONE else want's but's afraid to put the time and work into. Also, my current truck is a 2003 with 63,000 miles on it, so I really don't care about the mileage.... Would much rather have the coolness factor of driving something unique. You couldn't have explained it much better.... But to answe the first question, I expect to get around 10 mpg with my truck. New 330 hp crate motor (350), 4 wheel drive with 33" tires.

[CC69Rat]

Just to clarify, I am 39yrs old and I have owned 38 cars in my life time. A lot of new ones, sticker cars .. drive them off the lot and you loose $6-7k immediately. I just got tired of loosing my butt.

People want to push their trucks off a cliff when gas hits $4k a gallon, but want to pay $30k+ ($500-$600 mo) for a Prius because it saves 20mpg ? (no offense intended) .. I just don't get it personally. Do you know how much gas you can buy with $600 a month + residual loss in the new cars?

I'm as guilty as the next person, really. I bought a 2007 BMW 335 sedan 6speed a couple years ago because I had a (friggin sweet!!, perfect paint) 2007 Silverado Ext cab. polished 20's, flowmasters, etc. But I was afraid the gas would hurt me too much. I bought this Bimmer to be cool .. Yeah. $700 a month. 24Mpg on a good day. My truck got 18 or so. The bimmer was fast, but wasn't fast enough to outrun the depreciation! $36,500 - $20,000 when I sold it. $16,500 residual loss. (24 months I owned it. $687.50x24 ? = $16,500. I was SICK.

I just made a point, I would never loose my butt if I could help it. Everything I put into my trucks makes them better. When I made the payments on the BMW, I might as well have flushed it down the toilet. Proof:


So, for $687.50 per month I can buy 172 gallons of gas. .. or roughly 3100 miles a month and that's just the payment. Try insurance on a 335, maintenance costs, etc. It was a bonehead move for sure.

Never again.
Again, not trying to stir anyone up. Just my opinion. I've been there.

Kinda puts a new perspective on saving 2-3 mpg huh ?

[aventur1]

I get 8 to 10, mostly 8 because I like the sound and power so a little heavy on the peddle...ha...
Yep plates are 10 a year, insurance is 20 a month a water pump is 26 bucks and 3 beers later up and running...love driving my truck...no way am I going to any newer truck, I'll buy the gas and get thumbs up from lots of on lookers.

[Daddy Bartholomew]

71 GMC, 400sb, 700R4, 3.73 posi, late model Qjet that I tinkered with substantially - I don't really track mileage any more, but after I had everything together, I ran a hundred ten mile roundtrip as a test (ten miles in town, 100 highway) and used 5.5 gallons.

Good enough.

[c50rob]

1968 short bed with stock 350 crate engine, 3 speed and 3.07 rear gears, been averaging between 10 and 11 mpg doing mostly four lane highway between Elizabeth City NC and Portsmouth Va.

[Fldawg]

70 swb c-10 , 383, turbo 350, 3:73's = 8 mpg

[cleanfreak]

Tired 283 2bl, t400 , stock gears (3.73?). 14-17mpg .

[oldgold70c10]

Seems to vary with quality of gasoline.
Last tank ethonol free 16.1 mpg
Up to 10% ethenol average 14.5 mpg.

My set up:
rebuilt .030" over 305
9.3:1 flat top pistons
1977 Q-jet
TH350
3.07 rear end gears
225-75R15 tires
195-degree stat

I'm happy.

[PAWS 72]

350-.030 over-3.08 = 5-8 mpg 32 mile round trip running 50 to 60 mph.
Drove nearly 200 miles today to a car show and averaged about 14.6. Ran around 55 to 60 mph.why the big diffrence?
I bought a tach and it showing 2300rpm at 60 mph.Is that about rite for 3.08's?

[Fldawg]

Originally Posted by PAWS 72

350-.030 over-3.08 = 5-8 mpg 32 mile round trip running 50 to 60 mph.
Drove nearly 200 miles today to a car show and averaged about 14.6. Ran around 55 to 60 mph.why the big diffrence?
I bought a tach and it showing 2300rpm at 60 mph.Is that about rite for 3.08's?

that's about right, my truck with 3:73's pull about 3000 rpm at 55-60

[mechanicalman]

Originally Posted by PAWS 72

350-.030 over-3.08 = 5-8 mpg 32 mile round trip running 50 to 60 mph.
Drove nearly 200 miles today to a car show and averaged about 14.6. Ran around 55 to 60 mph.why the big diffrence?
I bought a tach and it showing 2300rpm at 60 mph.Is that about rite for 3.08's?

Something might have been sticking, like power piston in the carb. Did you see any black tailpipe smoke the day of the 5-8 mpg?

Mechanical advance in the distributor. Was it sluggish that day?

If it was brakes they would have went up in smoke.

You might have gotten ripped off at the pump, volume wise if you used those numbers to calculate.

Could have been also atmospheric differences, altitude, air temperature, grade, headwind, etc.

Actually, 32 miles is not a good sample, a different gas pump might have kicked out differently when you topped it off. I'd guess the 14.6 on the 200 mile sample is lots more accurate and I would not worry about it until I did another long sample.

RPM's sound about right.

[BenE]

71 C-30, 327 .030 over, RV cam, bulldog 4-speed, 4.11 gear. For years I got 10-11 but the carb never seemed to be right no matter how much I worked on it. Put a can of Seafoam in the tank, 5 miles down the road it was like driving a different truck! Now I get right at 13mpg. But I'm in the process switching over to a 700r to make it driver friendly for my daughter. We'll see how that changes my mileage.

[MrSchaeferPants]

305 V6/SM465/ no idea my rear end. 3.73-4.11 Never looked, no codes, tags rusty. I'm too lazy to raise and spin my wheel and count - 8mpg. I probably never go above 2000rpm, these don't rev high. i don't know what it cruises at, no tach. Usually around 55mph on the freeway, sometimes 60. Daily driver, but I don't drive much. Can't beat no car payment and liability. Could squeeze out around 2 more mpg, once I tune it up, and if the carb wasn't leaking.

[70cst]

Best of luck and we luv road trip pics