Fuel mileage

[TurboThrift]

The best I've ever had is a little more than 17 mpg in a '67 long bed with a 250, sm465, and 3.54 gears cruising at 60-65 with ~32" rear tires. That was on a 200 mile trip, though. Around town, I would get 12-15 mpg on average.. depending on the day.

[In The Ten Ring]

10 mpg is my estimate, 250 I6, 3 OTT, 4.11 gears.

[Eddie H.]

I have a 406 small block, TH400 and 3.07 gears in my 69 GMC.

I really don't know what kind of mileage it gets. I just know that I have to be sure and shut the engine off while I'm filling the tank, or else I can never get it full.

[Tkmadone]

I have a '67 C20 with a tuned port 305 and a 2004r transmission with 4.10 gears.

I check mileage every tank and average 14.6 in town and 16.8 on the freeway.

[tsetsaf]

Real world 5.3, 4l60, 3.73 with 32.5" tires. 45k overall average 17 mpg. Best was 22 mpg with a tail wind flat land cruise at 65. Worst was during the autocross I won .

16 gallon fuel tank and low fuel warning comes on at @280 miles. I have 50-80 miles at that point.

[gvw5400]

Mountain highway mileage, 14mpg. 350 750cfm 4 bbl. /465 3.73 with 29.5 rear tires.
Also 3"/5" drop
20 mpg. may be possible, but I don't know if overdrive in an auto trans is enough magic
to get there.
All the Best, Dirk

[bill3rail]

What is MPG? I know what this is in my 2012 daily driver, but those initials are foreign to my truck!

[Steeveedee]

Originally Posted by bill3rail

What is MPG? I know what this is in my 2012 daily driver, but those initials are foreign to my truck!

What, you use GPM?

[s10mk]

This is an interesting thread to me since I'm looking to buy my first 67-72 Chevy to use as a daily driver. I currently drive a 2012 gmc 2500hd with a 6.0, and I get a max of 15mpg on the highway. If I can do better than that with a 67-72, I would be a happy camper.

[Mike C]

Would be interesting for someone to maximize mileage with one of these trucks. 307 or 305 with a T5. Rear gear to match peak torque of the motor, FI to maximize lean cruise ratio, lowered to minimize air under the truck, air dam, narrow high pressure mileage tires, tonneau cover, etc. Maybe some Moon discs on the wheels.

I don't see why you couldn't build a 20 mpg at 55 or 60 mph truck fairly easily, but the odds of pulling that off at 75 or 80 go WAY down.

[Coley]

I always go with the 12-14 mpg angle on my truck....probably not too far off.
....that said, I'm not sure why this matters?

I do get the odd person having a giggle at the mileage angle on the older vehicles tho'....including my truck.
However, I tell them the extra amount of money I pay in fuel is partially made up in the vehicles yearly appreciation in value. Then I point out that their new vehicle is using approx. $10 a day in 'depreciation fuel'....on top of their regular gas costs....and payments...and insurance....and....lol.
Its hilarious how little people think of the fuel costs in relation to the overall costs of vehicles...lol....although that is what happens when people get hung up on the marketing of fuel costs being a super, ultra big deal.
Another analogy I use with people who spend a lot of money on a new vehicle...particularly to get better mileage, is that its like spending a million dollars on a new house because it has a more efficient furnace or heat pump than your old house....lol.

All that said, if I had to do some heavy duty daily long distance commuting....I would be using a great cheap used 4 cylinder car....maybe a Toyota or equivalent. Better to let that thing take the beating and the fuel hit....and save the classic vehicle for the regular enjoyable driving and use.

all good

Coley

[truckster]

Originally Posted by Mike C

Would be interesting for someone to maximize mileage with one of these trucks. 307 or 305 with a T5. Rear gear to match peak torque of the motor, FI to maximize lean cruise ratio, lowered to minimize air under the truck, air dam, narrow high pressure mileage tires, tonneau cover, etc. Maybe some Moon discs on the wheels.

I don't see why you couldn't build a 20 mpg at 55 or 60 mph truck fairly easily, but the odds of pulling that off at 75 or 80 go WAY down.

But at that point you're building a commuter car, and there are plenty of those around that get 35+ MPG.

[Signkutter]

I have a 72 3/4 ton 2wd 4:11 gears with a 700r4 , 350 with EFI 6090 aluminum heads and a mild cam . It doesnt get over 14 mpg on the highway and city is about 10 mpg. The engine has about 500 miles on it...so maybe that will improve as it breaks in....but it is never going to be a 2o mpg vehicle...unless its down hill

[67ChevyRedneck]

350/700R4/3.73. Checked a lot of tanks over quite a few years. 11-13 cruising around town (not a lot of OD use).

Highway looks something like this:

55-65 - 16-17mpg
65-75 - 15-16 mpg
75+ 14-15 mpg

She's a brick.... truck

Most the of time I average around 15-16 on highway trips, but 90% of my driving is the around town 12mpg.

My 65 Mustang really does get 20+ mpg, but it's over 1,000 lbs lighter, more aerodynamic, has less HP, less gear, but same OD gear!

[custom10nut]

What's all the hubbub about mileage? If one wants "good gas mileage", get a four banger, in a small truck or car.
How many 4-6000 lbs vehicles get "good mileage"?
I think I can get about 240 miles to a tank, on the highway, but just around town, back and forth, I don't even pay attention.
If I didn't have my truck, I'd have a hot rod with a warmed up power plant, and I'd be in the same situation. Of course I'd probably have more "invites to to the Policeman's Ball" than I've had with the truck. (0 by the way. )

[Steeveedee]

Originally Posted by s10mk

This is an interesting thread to me since I'm looking to buy my first 67-72 Chevy to use as a daily driver. I currently drive a 2012 gmc 2500hd with a 6.0, and I get a max of 15mpg on the highway. If I can do better than that with a 67-72, I would be a happy camper.

Dream on. These things have the aerodynamic configuration of a brick. Your 2012 truck is a way more streamlined brick, and has a lot of lighter parts and such. I get 7 MPG pulling my 26 foot travel trailer, and I don't ever expect that to improve. Maybe with a diesel, but that cost would never be recovered in my lifetime. Something to think about.

[In The Ten Ring]

Originally Posted by Signkutter

I have a 72 3/4 ton 2wd 4:11 gears with a 700r4 , 350 with EFI 6090 aluminum heads and a mild cam . It doesnt get over 14 mpg on the highway and city is about 10 mpg. The engine has about 500 miles on it...so maybe that will improve as it breaks in....but it is never going to be a 2o mpg vehicle...unless its down hill

I have the same truck, but 1/2 ton and 3OTT.

I once borrowed for a day a little Mazda 5 speed truck and it was pretty sweet....I'm sure it would do better in the mileage department but I love my old truck and I want to get it going again.

[tlman]

not sure about you guys but all our fuel is an ethanol blend here in Ontario Canada ,I just put my 1970 c10 with 350 /performer intake 650 holley 700r4 /3.73 and 285/55/20 tires .on the road and get 15 mpg ,I have not put the convertor lock up kit on yet im happy with that ,like someone said if mileage concerns you get a Honda
my daily driver is a 78 k1500 454 /performer air gap /800 eldelbrock /th 350 /2500 stall /3.73 and 31" Kelly safari ,I don't even look at mileage ,just glad I live within 3 miles of my job

[72peace]

ok so none of the sbc's can get to 20mpg, but what about the inline 6 trucks? Surely some of those have, maybe... Anyone chime in on those?

[dmw319]

350/th350 here and I get 9mpg, all city driving. It's my daily driver but I work close to home so no big deal for me!

[HO455]

Originally Posted by Mike C

Would be interesting for someone to maximize mileage with one of these trucks. 307 or 305 with a T5. Rear gear to match peak torque of the motor, FI to maximize lean cruise ratio, lowered to minimize air under the truck, air dam, narrow high pressure mileage tires, tonneau cover, etc. Maybe some Moon discs on the wheels.

I don't see why you couldn't build a 20 mpg at 55 or 60 mph truck fairly easily, but the odds of pulling that off at 75 or 80 go WAY down.

I'm confused. I have a 305 in my Burban, and I dont know where this torque your referring to is.
I have done a bit of looking at MPG ratings of later model trucks (1995-2013) in search of a possible donor vehicle and what I see is that mileage improvements all seem to revolve around transmissions. It looks as keeping the RPMs in the sweet spot is the key. (Like you would on a diesel.) Thus more gears and computer technology. Engine technology is not making any real gains at this point. You just can't cheat physics.