Poor Gas Mileage

[Jerry in Shasta]

Restricted exhaust or dragging brakes??

[Brother Hesekiel]

My roadster is driven mostly in town, runs like a Swiss watch, doesn't smoke or ill-behave at all, and the spark plugs look just like you'd want them to look. When at operating temperature, I can close the GAV completely, retard the spark all the way to the top, and it idles at 400rpm. My average mpg is about 12 as well. From what I've read over the years, that's not unusual for some cars.

[Bruce VA]

First, many thanks for all the help. Looks like I've got some more work to do: it only got 13 mpg today on the road trip. I'll be following up on your suggestions this week & see how it goes.

[mhsprecher]

I took a trip today in my 1930 town sedan. It was running great. The tires needed air (they were at about 30 psi) and in about 100 miles I got 16.9. I was quite happy with that. Mixed driving on a windy day.

[Fred K-OR]

Did you say you had a "Zenith B carb ". That being a B carb rather that an A carb? This could be your problem. I also have a "B" carb on my huckster and only get about 15 MPG or so. I am going to go back to an "A" carb and see if that makes a difference. I think it will.

[C26Pinelake]

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Last weekend on a 90 mile trip at about average 45 to 50 mph I got 21 mpg. Usually around town I only get 15.
Wayne

[super flat]

Originally Posted by sidevalve8ba

Bruce,

You mentioned ethanol spiked gasoline early on. I do not know what part of Virginia you call home but there are close to 300 gas stations in this state that sell non-ethanol gas. Click on this link and see if any are near you. I have seen a 10% improvement in fuel economy in my own vehicles by using non-ethanol.

http://pure-gas.org/index.jsp?stateprov=VA

I hope this is of some help.

I think if you can get non ethanol gas that will be your best improvement in mileage. Gary

[mshmodela]

I pulled my TT10 and they were fouled... I'm running WY16 for now, I believe a little hotter plug than a W18, which I have a set of those as well to see what a few months of driving starting next spring will show

[Purdy Swoft]

If this hasn't already been said, Model B carburetors are suppose to be run with the GAV closed completely after a brief warm up. Model A Zenith one and two carburetors are suppose to run with the GAV open 1/4 turn open after warm up. If the B carb won't run with the GAV closed after warm up, there must be a problem. I also recommend running Champion W 18 spark plugs. Motorcraft TT10 plugs are way to cold and you don't get full power from the fuel.

[CWPASADENA]

I have a 30 Tudor with a B engine, B carb and intake, 5.7 C.R. head and a Mitchell O.D.

With lots of stuff in the car and running along at 50-55 in O.D., on a recent 1500 mile tour, I would get around 18 MPG.

Very satisfied.

Chris

[jbond]

Our club takes trips where we travel together. On the last trip we were discussing what speed we were traveling at. No 2 cars reported the same speed and there was a 10 mph difference in what was reported. So maybe check your speedometer with a GPS unit or compare a 10 mile distance in the A with your modern car.

[mshmodela]

Motorcraft TT10 plugs, I believe work better for higher compression heads (a colder plug). I had then on my standard compression head and they were fouled. I'm trying WY16's now which are a hotter plug --if you have standard head, it might be worth a try..

[Charlie Stephens]

Originally Posted by Bruce VA

Need some advice on improving the gas mileage on my A Model (1929 Tudor w/ a Zenith B carb on a 31 engine) First, my odometer has been checked; it works fine. I have no fuel leaks. The car starts & runs fine. I start it cold w/ full choke, GAV 1 turn out, spark fully retarded. As soon as it starts, GAV to ¼ turn out, spark to ¾’s down. I rarely move the spark advance from ¾’s as I rarely exceed 45 mph. Timing is dead on. The timing pin fits easily in the slot in the gear; trailing edge of the rotor is just opposite the #1 tit in the distributor as points just start to open as observed w/ a meter. (I gained about 2 mpg after adjusting this) Timing confirmed w/ a light & marks on the crank pulley. Points set at .018 & confirmed w/ a dwell meter at 31*. Advance works as it should by observing the timing light. Plugs are a light brown. Not that it needed it, but carb was soaked in cleaner, blown out & rebuilt w/ all new flow tested jets, nylon jet gaskets, etc. Carb idle was checked w/ a vacuum gauge. Float level checked w/ a plastic tube; 5/8” from the carb seam. What can I do to improve the current 12 m.p.g. gas mileage? Thank you.

Bruce,

Have you checked your odometer? AAA used to have a mobile unit that went from one office to the next and checked speedometers and odometers.

Charlie Stephens

[P.S.]

Each of these things made a small improvement in MPG on my Tudor sedan. All combined, it went from 15 MPG to 20+ MPG on the highway (no overdrive).

1. Swapped in a rebuilt motor with insert bearings.
2. Snyder 5.5 head.
3. Zenith 1 carburetor rebuilt by Bert's.
4. Switched to Champion 3X spark plugs.
5. New manifold gaskets, used "goop" on block side to seal them.
6. Inflate tires to 35 PSI.
7. Swap out drums that dragged on brakes occasionally in rotation.
8. Removed all unnessesary weight from car (removed trunk rack, etc.)
9. Changed shift points to about 10 MPH 1-2, 25-30 MPH 2-3.
10. Switched to synthetic motor oil (flak proof suit on!).
11. Switched back to stock ignition (original style points).

[Chuck Sea/Tac]

No one has asked this. What your rear end ratio?

[Brobrian]

This discussion always gets me down. I feel like Bruce, that I've done just about everything to properly tune and to reduce drag, but get 9 or 10 mpg, and have for 25 years.

[Tom Wesenberg]

Originally Posted by Brobrian

This discussion always gets me down. I feel like Bruce, that I've done just about everything to properly tune and to reduce drag, but get 9 or 10 mpg, and have for 25 years.

That's due to California smog. You need to burn clean air.

My 28 stock Phaeton gets 22 MPG on the open road, but only about 17 in town.

[tbirdtbird]

download the speedometer app to your phone and run with that for a while. these stock speedos are not as accurate as you think.

[Brobrian]

Originally Posted by Tom Wesenberg

That's due to California smog. You need to burn clean air.

My 28 stock Phaeton gets 22 MPG on the open road, but only about 17 in town.

Yup, Tom, motor has to work hard to chew up all that smog. Have to burn Cal. gas with ethanol, and whatever additives as well. I don't really complain, though. I put a few thousand miles on each of my A's last year and feel blessed to have been able to to it. I'd probably drive them just as much if I got 5 mpg.

[mshmodela]

Likely due the gasoline requirements of the California Republic... Less Energy per gallon than 100% gasoline.