49 Buick Roadmaster - gas mileage

[Sir John]

Can anyone tell me what your expereince is in fuel consumption / gas mileage for a 1949 Buick Roadmaster Convertible?  I think I'm having a fuel line leak, as I filled the tank (it holds 19 gallons), drove about 140 miles, stored the car in its garage for a week, and then the car would not start.  We added about 5 gallons of fuel to the tank and it started, but I can't believe the tank was empty.  I haven't driven the car more than this before and have not yeet had a chance to measure its gas mileage.  Your thoughts?

Thanks.

 

[rocketraider]

That averages to 7-1/2 mpg assuming the tank was in fact empty below the fuel pickup. Even a big heavy Roadie with a DynaFlow should do better than that.

 

If you were losing fuel to a leak, you'd smell it in the garage. I think you had some high-volatile fuel that actually evaporated from the carb and tank. Not unheard of with modern gasoline formulations that are blended for fuel-injected engines.

 

If you have access to non-ethanol fuel, use that in your Buick. Even 87 octane should work fine due to the engine's comparatively low compression ratio. Fuel mileage should increase and the volatile component should not evaporate as quickly.

 

But probably a good idea to look over the fuel system from tank to carb to verify there are no leaks, and to replace rubber fuel lines with modern alcohol resistant materials as a matter of course.

[Rusty_OToole]

Gas mileage in the single digits was not out of the question for one of those. Big, heavy car, massive straight eight engine, one speed Dynaflow transmission with slippy torque converter. On the hiway at a steady 50MPH might be good for 12MPG or a little more but in traffic 8 - 10 would be typical.

You could change to synthetic oil, tune up the engine, pump up the tires but it's never going to get great mileage especially on the watered down slop they sell for gas these days.

[m-mman]

 

Beware that a fuel leak might not look like a leak. Between drives (weeks to months) I simply could not keep fuel in my 1929 Cadillac. It was stranded on the road several times. 

 

Turned out that in two different places fuel was NOT DRIPPING but coming through a small crack and through a bad O ring. The leaking fuel would spread out over the surface, look a little moist in the area and then evaporate. Nothing on the ground. No drips or drops.

Drove me crazy trying to find it. A new O ring and some goop stopped them up, no more problem. 

Edited April 23, 2021 by m-mman (see edit history)

[Sir John]

Okay - thanks, all.  It doesn't help that the gas guage doesn't work.  I understand that the fuel could have run out, but it doesn't sound likely. There are no fuel smells or drips, but I'm going ot have the fuel lines and tank looked at to check for anything obvious.  

Thanks again.

[rocketraider]

11 hours ago, Sir John said:

It doesn't help that the gas guage doesn't work.

😳

[Rusty_OToole]

In another thread, owner of a 1938 Buick Roadmaster reports that he got 11.3MPG on a hiway trip. Do any other Roadmaster owners know what kind of mileage they get?

[61polara]

Several years back a friend and I were driving a 1947 Roadmaster (manual transmission) and a 1957 Roadmaster to an AACA National six hours away, mostly interstate.  The 1947 averaged 17 mpg and the 1957 16.5 mpg.  However the pickup tube on the 1947 is short and gas stops were needed whenever the gauge fell just below half a tank.

[Larry Schramm]

I have been told that 10MPG +- is not unheard of for these cars. 

 

I have a bunch of older cars and I always plan on gas stops based on 10MPG +- just a little bit.  If I get better fuel economy, then I am a 🙂 guy.

[autoluke]

I often drove my dad's 1948 Buick sedan ( with Dynaflow ) after he turned in his license, and was always paying attention to the location of local gas stations.

 

Best I can remember was ten miles per gallon .

[Dynaflash8]

On 4/22/2021 at 5:04 PM, rocketraider said:

That averages to 7-1/2 mpg assuming the tank was in fact empty below the fuel pickup. Even a big heavy Roadie with a DynaFlow should do better than that.

 

If you were losing fuel to a leak, you'd smell it in the garage. I think you had some high-volatile fuel that actually evaporated from the carb and tank. Not unheard of with modern gasoline formulations that are blended for fuel-injected engines.

 

If you have access to non-ethanol fuel, use that in your Buick. Even 87 octane should work fine due to the engine's comparatively low compression ratio. Fuel mileage should increase and the volatile component should not evaporate as quickly.

 

But probably a good idea to look over the fuel system from tank to carb to verify there are no leaks, and to replace rubber fuel lines with modern alcohol resistant materials as a matter of course.

Cousin had a 49 Roadmaster convertible back in the 1950s.  It was getting about 6 mpg, so he traded it on a Chevrolet.  What can I say?  I'm a Buick guy myself, but that's a fact.  He was in the military at the time and couldn't afford the gas.

[Ray McCaskey]

On 4/22/2021 at 11:59 PM, Sir John said:

Okay - thanks, all.  It doesn't help that the gas guage doesn't work.  I understand that the fuel could have run out, but it doesn't sound likely. There are no fuel smells or drips, but I'm going ot have the fuel lines and tank looked at to check for anything obvious.  

Thanks again.

 

On 4/22/2021 at 11:59 PM, Sir John said:

Okay - thanks, all.  It doesn't help that the gas guage doesn't work.  I understand that the fuel could have run out, but it doesn't sound likely. There are no fuel smells or drips, but I'm going ot have the fuel lines and tank looked at to check for anything obvious.  

Thanks again.

 

[Ray McCaskey]

I have the same issue on my 49 Buick.  Tank was 3/4 full setting in garage for a month and tank was completely empty.  No smell in garage and tank appears solid on bottom.  There has to be a leak somewhere.  What did you find?

 

Thanks,

 

Ray

[JACK M]

Maybe a neighbor kid with a syphon hose.

Not sure just why that entered my mind........Tastes terrible.

[arcticbuicks]

@Ray McCaskeyi would try a locking gas cap first ......and check in a month again  ?

[Ray McCaskey]

The car is in a locked garage and the tank was completely empty.  The fuel line does not connect to the lowest part of the tank.  How does the gas get from the bottom of the tank?   Is there a vacuum that pulls the gas from the bottom?

 

Thanks,

 

Ray

[61polara]

29 minutes ago, Ray McCaskey said:

How does the gas get from the bottom of the tank?   Is there a vacuum that pulls the gas from the bottom?

Your fuel pump creates a vacuum to pull the gas out of the tank.