Last month, we posted this question and answer in Ask Hagerty:
Q: I recently purchased a nice 1950 Chevy Coupe with Powerglide. It's a great car but takes gas like a hog going to slop. Is there anything that can be done to improve the mileage?
A: For starters, change the engine oil and filter and the transmission fluid (after a flush). We'd also recommend new points, plugs, wires, setting the timing and changing the air filter. Next, check to make sure no brakes are dragging and that the tires are properly inflated.
Unfortunately, once those steps have been taken, there's little more you can do.
Afterward, we received many e-mails from members offering additional advice, further proof that one of the most valuable resources for car guys is other car guys. With almost 250,000 members, Hagerty Plus is the largest community of enthusiasts – and potential resources – out there. Here are their comments:
“I thought you were a bit brief on the suggestions in regard to that person's fuel economy question. If someone was really interested in getting the best fuel economy, in addition to what you listed you could have suggested:
- Run the tires about 3 p.s.i above listed pressure. The extra hardness won't really affect handling or performance but will give slightly less rolling resistance. And what type of tires are on the car? Bias-ply or radial? Are the tires too wide? It’s a modern trend but one that can lower gas mileage on a car not driven very often or ‘hard.’
- When was the carburetor rebuilt? If it’s a ‘50s carb, is it still working as effectively as possible?
- How about a top-end overhaul? Shave the head and raise compression slightly. Smooth out the intake manifold and make sure there are no burrs or flanges in airflow - these mods are normally done to increase performance, but based on tuning will also improve mileage. Modern gas is better quality than 1950s stuff. Use its better anti-knock and burn capabilities.
- If you're not worried about total originality, how about installing an electric radiator fan and removing the belt-driven fan? That frees up horsepower.
- Were any alternate gear ratios available for gearbox or rear axle, maybe from a different model? You may want to accept slower acceleration for better cruising economy with lower engine revs on today's highways.”
“In reference to your reply on the ‘50 Chevrolet coupe with the poor gas mileage, other problems could be improper carburetor choke adjustment or operation, carburetor float adjustment or float replacement, carburetor main jet size. Also vacuum leaks could be a problem, distributor vacuum advance and centrifugal weight adjustments. Another problem could be the exhaust. The muffler could have broking baffle plates causing restriction. Also engine performance should be checked for compression and loss of power.”
“RE: the gas mileage question from the guy with the 1950 Chevy, the first thing a professional mechanic would do is put it on a meter and see what the CO is. Maybe it is running way too rich. The other things are sound maintenance advice but you should start with knowing whether or not the mixture is correct. Comparing actual mileage to known figures would be a good idea too.”
“Good answer, but you missed five things.
- Check vacuum advance diaphragm to verify that it holds vacuum.
- Check to see if it is getting vacuum and it advances.
- Verify that the mechanical advance is functioning correctly.
- Clean and rebuild carburetor.
- Try adding SPT gas treatment to fuel once a month (good for older engines).”
"I had a ’52 … my first car in 1959…great car. I was 16 and had a lead foot and got 17-20 mpg. The secret to that car (Powerglide) is all in the tuning. Set the points and then use a timing light and set the timing 2 degree advances and also use a vacuum gauge for maximum vacuum at idle. If you are a lead foot, shift from Low to Drive manually at about 25 -- 30 mph.”
“If he removes the fan and replaces it with an electric fan, it will save 20-25% in gas. Keep all the old fittings and replace for concours etc.”
“Being a very old guy and old Chevy fan, tell the guy if he wants better gas mileage to put a fuel regulator between the fuel pump and carb on that particular car.”
Please note: Any advice, recommendations, or opinions offered above are solely those of the author and should not be considered advice, endorsement, or a recommendation from Hagerty.