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Gas mileage survey and discussion

12K views 94 replies 49 participants last post by  junkyard junkie 
#1 ·
With the price of gasoline having reached new heights this year, gasoline mileage is becoming a consideration to those of us that drive vehicles not known for thrifty consumption.

What I would like to know is what you all are getting as highway mileage in your particular combination. And what strategies to use to maximize fuel efficiency. Anyone run a blower and documented mileage change?

Before swapping in a 3.42 gear, my 2.41 geared Pontiac 455 (9.25:1) Trans Am neared 16 mpg. I have not accurately measured it with 3.42s but expect around 12. Will retest soon.
 

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#3 ·
My 383 chevy in the 36 PU gets 21 cruising at 70 with A/C. It has EFI, overdrive tranny with 3.36 gears but only weighs 2600#s. The bad news, I have to burn premium. The 36 Coupe gets right at 24 same cruise conditions, overdrive tranny, 3.36 gears. It has EFI on a 327 and weighs within 50 pounds of the PU. I burn regular in it. I planned ahead for the higher priced gasoline that had to come but probably will never recoup the cost of the EFI from fuel savings. But doing away with the carbs is worth it to me.

Trees
 
#5 ·
With the price of gas coming down this may be a moot point but I'll toss in my .02 cents...
My '92 Astro (all stock & 231K) gets almost 23 mpg...
My '95 GMC Sierra (mid-length headers, Jacobs Pro Street ignition, TB Spacer, etc.) gets over 25mpg if I go easy on it.
My '00 Monte SS gets between 25 & 26 mpg.
These are all O.D. trannies which makes a big difference mileage wise.
Swapping to an OD trans would help your situation AND improve off idle times.
Mark
 
#6 ·
roller 302 in a 46 pickup..coming back form Louisiana last trip. 80+ mph, air on got 21 mpg Should do better with some tuning. :D
made a trip to arkansas sunday in the 69. 75-80 most of the way. coming back, was loaded with about 900 lbs of motorcycle & parts...avg 16 mpg
 
#7 ·
I get 8 to 8.5 mpg city with my 1970, LWB, 1/2 ton truck, with AC on.
And 13 to 14 mpg highway at 70 to 75 mph.

454 bbc, 8.75:1 cr, 206/212 roller hyd. cam, th400, 3.08 gear, 1500 stall, thorley tri-Y headers, 750 holley vac secondary, 4200 lbs with driver, 275/60-15's all around, and 4/6 drop.

It still amazes me how much fuel a BBC uses even while driving slow.
 
#9 ·
454C10 said:
I get 8 to 8.5 mpg city with my 1970, LWB, 1/2 ton truck, with AC on. And 13 to 14 mpg highway at 70 to 75 mph.
I get about the same on my 79 c-10/454/4-spd

I just did a guestimate on the 59---only 13 :rolleyes: with a Tremec 5-spd.
But I'm still getting things worked out on it.
(might have to have 454 c-10 guy come and work on it :D )

Bryan
 
#10 ·
Some guy asked me once...

How much better gas milage did the old 6-bagger's get than the V8's we drove back in the 60's? First off I told the Dude there is no such thing as a 6-bagger..its a 6-banger for 6-cylinder engines and there is no way I could compare with the V8's as I never drove a 6-banger to compare it to. We really wern't concerned with gas milage aback in the 60's so only people who really wanted a 6-cylinder car drove them. Not everyone was into muscle cars...even back then!! I remember the 4-banger Pinto's...we had fun dropping in a V8sbc into those pony cars!!


Tazz
 
#11 ·
astroracer said:
With the price of gas coming down this may be a moot point but I'll toss in my .02 cents...
My '92 Astro (all stock & 231K) gets almost 23 mpg...
My '95 GMC Sierra (mid-length headers, Jacobs Pro Street ignition, TB Spacer, etc.) gets over 25mpg if I go easy on it.
My '00 Monte SS gets between 25 & 26 mpg.
These are all O.D. trannies which makes a big difference mileage wise.
Swapping to an OD trans would help your situation AND improve off idle times.
Mark
Yea gas won't be going up ofter the election now will it.
 
#12 ·
I remember dad buying a 6 ganger 63 Dart because it was cheaper than a bigger car with a V-8. He liked bigger cars and big motors but at that time, all we could afford was the lower line car. I remember him saying it got 25 on the highway running 70 with a 170 cu in /6, 3 speed stick and who knows what gears. Probably a 2.94. My 66 Belvedere /6 auto had 2.94's so I assume maybe so did the Dart. The Belvedere only got about 16 in town with some highway going back and forth to work driving the snot out of it. My 3/4 ton Dodge diesel gets 19 in town if I'm nice to it but goes to 17 if I push it some and 24 on the highway if I keep it around 70. Mileage goes away fast when the rpm goes over 2000. It has 3.54 gears. The Durango with 3.90 gears gets 16 at 70 and 12-13 in town, 318 engine.
 
#13 ·
tm454 said:
How much better gas milage did the old 6-bagger's get than the V8's we drove back in the 60's? First off I told the Dude there is no such thing as a 6-bagger..its a 6-banger for 6-cylinder engines and there is no way I could compare with the V8's as I never drove a 6-banger to compare it to. We really wern't concerned with gas milage aback in the 60's so only people who really wanted a 6-cylinder car drove them. Not everyone was into muscle cars...even back then!! I remember the 4-banger Pinto's...we had fun dropping in a V8sbc into those pony cars!!


Tazz
well, 200 I6 powered Mustangs and Falcons of the 60's get between 20-25 MPG depending on condition and gearing. my '67 gets approx 21 MPG.

I'v read old reports that '51 Chevys got 15-18 MPG with the 216-235 I6's. Good for me, cause it won't cost too much to drive my '51 Chevy.
 
#16 ·
Forgot one, a 74 Dodge 1/2 ton swb with /6, 3 speed stick, 3.55 gears with 235/75-15 tires. This truck had nothing else besides a heater. Normal driving usually netted around 14-15 intown and around 17 on the highway but one time (and only once) I drove it with that egg under the gas pedal and got 21 with a combo of highway and in town driving. Man, that was the longest week I ever had! Speeds never got over 55 and was passed by everyone!
 
#18 ·
Gas Milage

During the 60s not all of us were rich enough to waste 32.9 per gallon regular and had to pinch pennies to keep food on the table. My 66 Belair 250 L6 with P glide got 17-18 in town and 20-22 on the highway (I kept pretty good records on this car for taxes). running the AC sucked more gas so it stayed off unless the heat got completely unbearable. At teh time my neighbors 62 Belair 283 2bbl "three in the tree" got close to the same. My 66 Impala 327 4bbl Pglide got about 14 but I ran the ac all the time (I got a better Job).
Now that I'm rich and famous (LMAO) my 66 396 SS (completely stock 396 325hp with th400 2.73 gear) gets combined mileage of 16 for easy cruising. It's a convertible so I almost never turn on the AC.
 
#19 ·
57 T-Bird 312/300 AOD 3:56 always 20-22 mpg
When it had the Fordomatic and 3:10 13-15 mpg.

69 Judge Ram-1V 4 spd 4:33 on a great day 10-11 mpg.

67 vette 427/435 4 spd 4:11 never over 10 mpg.

63 Vette 327/350 4spd 4:11 18-20 all day.

Right now only have the bird and some 454 vettes but not driven the 454's enough to know. Can't be good!

Not sure why I torture myself but with every car keep a running log of mileage.
 
#20 ·
I have to run premium but I get 14 mpg on the highway and 10 in town with a high compression 427 a 700r4 with .70 over drive 4.56 gears and 31x10.5 tires on my 6000lb 58 apache truck.The truck got 16 on the highway and 7 in town with 3.73 gears.I drive it mostly in town so the lower gears allow me to feather foot it around with excellent acceleration which is important in traffic.
 
#21 ·
86 Monte Carlo SS,Comp Cams solid roller equipped LS-6 454 Big Block,Doug Nash 4+1 Five Speed,3.28:1 first gear,3.00:1 rear gear ( 9 inch Ford ),15-17 MPG on the highway,and thats cruising at 10-20 over the speed limit,but if you drop the hammer real hard,you can watch the gas gauge drop!It might get better if I really tried to drive for economy,but thats pretty hard to do!
 
#22 ·
Rearend ratio vs. gas mileage

Modern V8s can get outstanding mileage - in the high twenties, such as my Lincoln Mark VIII w/ 4.6 DOHC has seen a best of 27 mpg - a combination of slick aerodynamics and tall gears.

But, if I understand correctly, there is a point of diminishing returns in taller gears, probably due to incomplete combustion at very low rpms. Isn't efficiency a bell shaped curve where if you run too tall a gear, or corresponding too low rpm, fuel consumption actually increases? So, following this line of reasoning: wouldn't you want to maximize efficiency at low rpm to achieve better highway cruising gas mileage? and what strategies could one use to this end? Any experience in this area?

Great discussion and listing of mileage results so far. Any blower cars?
 
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