What MPG Should a '49 Roadmaster Produce?

[SBRMD]

1949 Sedanet: 36k actual, new WWW radials, complete tune-up w/ all parts replaced, carb rebuilt w/ kit from Bob's. Runs oh-so-sweetly, like a Buick should. Handling city traffic and highway speed w/ absolutley no problem.

Mixed use MPG: ~9.7 MPG!!!

OUCH!

Any insights from the learned?

Thanks in advance,

Steve in Mpls.

[Guest brh]

Don't know but I feel your pain, had a 72 Centurion on a good day mixed travel 10 MPG. But gas was way cheaper then and it had a 455. Thats a lot of car but I would think she'd get better than that. Ya sure the trans isn't slipping or clutch worn. I know it shouldn't be at 36,000, but ya never know.

[Mark Shaw]

Yeah, keep your foot out of it!

Buicks are heavy cars and will get much better mileage if you don't jack rabbit the starts.

Your mileage should improve 10% or more if you don't try to keep up with the rice burners when the light turns green.

[Aaron65]

I'd say you're right about normal--unfortunately! Set her on the freeway at 60 though and you can do 15+.

[Guest brh]

Only other thing I thought of is to make sure your choke is not staying on too long. Any black residue on the exhause or black smoke means its too rich.

[SBRMD]

No black smoke...

No jackrabbit starts. With this car? Are you kidding? I don't start it in low, either.

Any other thoughts?

[Mark Shaw]

Are you using real gasoline or an ethanol mix?

Check your timing to make sure your spark advances at high speed.

[MarkV]

0 MPG if it doesnt run! LOL!

But, seriously, It sounds like a great car! You lucky person! Do, you have any pics. to post?

[Guest BJM]

I don't know - 10 to 12 mpg sounds right. It's big and heavy with a slushbox of an automatic that wastes gas/ineffiecent.

As a general topic, this would be great for all Buick owners from the 30's to the 80's because I don't remember a comprehensive survey of real world gas mileage for old cars.

They always say gas was so cheap back then but incomes were lower, etc - so nobody wanted to spend a lot filling up the tank. But there seemed little push to increase fuel efficiency until the 1970's.

[Bill Stoneberg]

I get about 12 on my 47 Super but it has the manual transmission.

Dont forget those cars had rear ends with gears meant for stump pulling not cruising.

My 47 for example has a 4.44 to 1 ratio while my 50 with a Dydnaflow has a 4.11 to 1.

[serb]

I only checked my mileage one time when we first got the 1946 Super, it was doing over 18mpg. That was mixed highway and city. We are going to a show in the south ski area in a couple of weeks, I am going to fill it up and check it again.

Results to follow.

Stevo

[The Old Guy]

I changed the rear end in my 40 super convert from a 4.4 to a 3.4 , and get 15=17 MPG on the highway

[SBRMD]

I'm using 100% gasoline, no alcohol.

Good suggestion about the timing advance, I don't think we dealt with that when we put in the tune-up stuff. I'm exposing my ignorance, here, but how does the advance come in on the '49? Not near the car right now; I'm not visualizing a vaccuum-advance unit...

Joe, you've told this before, but I don't remember: which years/models will donate 3.4 gears for the torque-tube rear? My current gears are 4.1:1, std for Roadmaster w/ Dynaflow in '49. Wonder what the change would mean for increased mileage vs. lost off-the-line performance (which is already pretty stately) in a Dynaflow car (I assume your '40 is a stick).

Thanks again in advance (no timing pun intended),

Steve.

[The Old Guy]

Steve

The 53-55 V8 dynaflow Buicks have 3.4-3.6 ratios. You may have to change the drive shaft and torque tube and use the one from your car, as some are longer than others. This is a simple swap as they did not change anything , even the side gear splines from 40- to 55

I also installed a 263 (1953) in my 40 and it keeps up with traffic quite well.

[JohnD1956]

Is the 56 rear end that much different? according to my manual the 40 series had a 3.23 in the dynaflow cars, and the others had a 3.36 for the dynaflow. The stick shift 40 series had 3.91's.

[The Old Guy]

The 56 rear end is a different design, and will NOT interchange ,unless you switch the complete unit from hub to hub. I have never seen it done, so there may be issues with the attaching arms.

[JohnD1956]

I should have edited my original post. I remembered that the 56 used common tube shocks while prior cars used the knee action shock absorbers. Not insurmountable. I guess the question is will the carrier and gear sets fit into a 55 rear axle?