gas mileage??

[PeteBell68]

To be honest I've never checked and don't want to know it's a toy .
I do know every drive even a short one is at least 20 .
Just keep filling it up .

 

[Dibbons]

What would really be fun is to swap in the AX15 five speed from my '96 Dodge Dakota Pick-up: AX15 = 3.83, 2.33, 1.44, 1.00, 0.79, 4.22R With it's hydraulic clutch, it could be done.

 

[mopar 3 B]

With 2.76 gears od will not help at highway speed. The 318 will run out of juice.

 

[mopar 3 B]

Completed a 4,600 mile road trip in a similar car this fall ('72 Satellite Sebring Plus, 318 CID, 904, 2.71 8 1/4 rear end) Gas mileage was 15, 16, 17, 18 with an overall average of 17.3 MPG. I don't believe mechanically you can increase that much more. Cruising at about 70 MPH (non-stop) seems to net the best mileage. But I am also always looking for ideas to increase gas mileage so my eyes and ears are wide open (my road trips are extensive).

As a comparison, my parents new/factory stock 1971 Road Runner 383 auto with 3.23 averaged about 12.5 MPG.

View attachment 540662

Some thing must not have been right.
Have a modified 383 in same combination with 4 spd 3.54 and get 16 mpg at 70

 

[Dibbons]

The Dakota has 3.55 and a V-6 (3.9L), so a 318 probably is maxed out at about 2.71/2.76 anyway.

 

[Dibbons]

I don't want to say I don't believe better MPG claims, but something outside the norm makes me wonder what the secret is? An almost 5,000 mile trip of careful monitoring has to be a little more accurate than a couple of tanks of gas here and there. And I forgot to mention, I deducted 10% in MPG figures because of odometer error, as well. And 2,000 miles of the trip was on the Baja Trans-peninsular Highway (see youtube clip):

 

[RT K_line]

I think your doing pretty good as is, my 92 pathfinder (daily driver) gets 17/18 with a v6 and isn't as cool as a mopar.

 

[kiwigtx]

hello all.i know most guys are looking for more power but i am looking for better mileage.i have a 68 satellite convertible that i take trips with.it has a stock 318 2 barrel with stock cam,stock exhaust manifolds,dual 2 inch exhaust,8.75 rear with 2.76 gears and 904 trans.it gets 16-17mpg on the highway.should i be happy with that or should i try to do better.i have 2 thermoquads i was thinking of trying. a 9185 318 truck carb and 9801 mopar universal thermoquad with electric choke, and edelbrock performer intake.i dont mind messing with it because i can always go back to how it was.thanks for any input.

Do you have any pictures of this car? We have some really cool members in Long Island also - maybe you might have run into some of them at a show or gathering.

 

[Fran Blacker]

Changing a trans for mpg does sound worth it. If your mileage jumped from 16/17 mph to 24 mph and drove you 160 miles is 10 gallons of gas. 160 miles at 24 mph is 6.7 gallons. You save 3.3 gallons at $3 a gallon that's $10 in a 160 mile trip. How much do you have to spend to get to 24 mph? If you spend a $1,000 for trans installed you need to drive it 16,000 TO break even.

 

[HawkRod]

I love overdrive transmissions to make driving at highway seeds much more comfortable. I doubt, however, that if you do it merely to save money, I doubt you will recoup your investment.

What I worry about in your case is that you have a 2.76 rear with a 318 2 barrel. I am not sure an overdrive is right with the gearing and power you have in your car...

 

[Wrenchero]

i guess i shouldnt complain too much.it runs great,super low maintenance, and it runs great on 87 octane.i met a guy at a show with a challenger with a 2bbl 318 challenger who got over 20mpg.he told me i should put a 7 1/4 in it.too bad i threw one out 25 years ago??

 

[Wrenchero]

i have a set of 3.23's but not sure i want to cut up the crossmember to put an overdrive in it.i wouldnt mind spending the money because i put about 3-4 thousand miles a year on it

 

[Kern Dog]

What would really be fun is to swap in the AX15 five speed from my '96 Dodge Dakota Pick-up: AX15 = 3.83, 2.33, 1.44, 1.00, 0.79, 4.22R With it's hydraulic clutch, it could be done.

That first gear is practically useless in a car. A truck needs the mechanical leverage to get a heavy payload moving, a trailer, etc. A car? No.
Besides, every engine has a point in the rpm range where it is the most efficient. Most stock classic car engines run efficiently in the 2000 to 2400 range. If you gear it to run at 1800 rpms at freeway speeds, it may not get any better mileage. If the factory thought they would run best at 800 rpms at 65 mpg, they would have a 1.5 final drive or something like it.

 

[JimKueneman]

68 Coronet 318, 904, 2.94 gears, 340 cam, Edelbrock Performer, FiTech EFI. 13.5MPG mixture of 2 lane and 75MPH+ Interstate driving is the best I can do. Be happy. It takes so much energy to keep these moving down the road and those old engines were not very efficient compared to today.

 

[Dibbons]

That first gear is practically useless in a car. A truck needs the mechanical leverage to get a heavy payload moving, a trailer, etc. A car? No.

Kern Dog is right about the first gear, but for bracket racing (But I'm not recommending the AX15 for that) it works out kinda neat.

ergo: The AX15 3.83 low gear combined with a 3.09 rear end ratio is the equivalent of an A833 with a 2.60 low gear and a 4.56 rear end (11.83 vs 11.86)!

 

[metaldad]

68 coronet 500 convertible, w/440 & 727. 390 sure grip, holley 4780 carb, edelbrock7186 mannyfold.
with the top down, on the eway for 120 miles @80mph, not punching it, 9mpg

 

[Dibbons]

Now that I can believe metaldad, something like Hemi mileage (and punch) I imagine.

 

[metaldad]

Now that I can believe metaldad, something like Hemi mileage (and punch) I imagine.

it's alot of fun to drive her

 

[Ranger16]

I brought my '69 Road Runner (383) from 14 to 16 by leaning out the carb a bit.

That said, 16-17 on a '68 carbureted V8 is probably nothing to sneeze at and would (in my opinion) be close to the best you'l do. As mentioned earlier, "Be happy".

 

[JimKueneman]

Here is a very good paper on fuel economy and what parameters effect and maximize it.