I am trying to take a fresh look at my high fuel consumption and would welcome the forum's input.

I log my odometer and fuel consumption on a spreadsheet.  My cumulative average since 2013 is 10.8 mpg.  On most tanks, I do between 10.2 and 11.2 mpg regardless of driving style or speed.  I usually drive economically.

Using google maps on a recent 53 mile trip, I calculate my odometer error at 1%, so I believe my fuel economy numbers are accurate.

I have tried many things, made many improvements to the car such as rebuilding the front suspension and getting an alignment, altered timing, advance curve, carburetor settings, etc yet tank after tank I see 10-12 mpg.

Performance is good.  The car feels responsive, smooth, quiet.  There are no drivability problems.  All the numbers I have checked (compression, vacuum, timing) at various points over 2 years have been in the prescribed range either by the manual or this forum.  So, I am pretty stumped as to why I am not seeing the more typical 14-16 mpg out of my Fairlane.

I'm not quite ready to accept that this is good as it's gonna get.  I am hoping this discussion will either improve my economy or show me I'm going to have to accept it as is.

Where should I start?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

What about one or two bended pushrods or clogged valves?


Hyvinkää, FI

How do the plugs look?

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

I would start by noting the rear axle ratio, tire sizes. Then the tune up.
If everything is in order (Compression/Timing/Carb jetting)?
Automatic? Loose torque converter?, Trans slippage?
Tire pressure?
Things I'd start to look at

Here is the requested information:

Axle: 3.10:1 original 9".

Tires: I have done many miles with both 225/70r14 radials at as much as 40 psi AND 7.50x14 bias plies at 24 psi. No difference in economy.

Compression: checked a couple of times since re-ringing engine, though not recently. All cylinders were within a few psi of 150.

Timing: I've been all over the map with this, checked the curve, changed vacuum advance rate, tried running with and without vacuum advance, road tested different settings with a vacuum gauge, etc. I could tell a difference in power, responsiveness, smoothness, pinging based on the different settings I tried, but none ever gave me a tank better than 12.5 mpg.

Carburetor: original carter afb with vacuum secondaries, correct stock jets and metering rods, correct float settings. I have tried 2 of these units, tried small adjustments to float level, made sure choke works properly, air bleeds are clear, etc. with no change in economy.

Transmission: original fordomatic. Bands adjusted, fluid type fa, removed torque converter and replaced seals a while ago because the converter was leaking badly(it's a bolt-together unit). Trans shifts well, no performance complaints, no slipping, tachs 3000 rpm at 70 mph, I don't think the converter is slipping more than normal for a non-lockup unit.

Engine: running 20w-50 oil. Engine runs hot at highway speeds, I believe due to poor flow through radiator which has clearly been patched up. Always stays in the normal bar on the gauge though.

Spark plugs: here are some pictures of 3 different plugs I pulled. Most show a pink residue which I'm told is from a fuel additive (I usually run shell regular). The first 3 are one plug at different angles, the next 2 are of a second plug, an the last 2 are a third.


1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Here are just a couple of things to consider; My wife and I just finished an 1,800 mile motorcycle trip. Up from southern California to northern Idaho and back. You can't feel it in a car, but on a bike, head winds and tail winds affect gas mileage. Stop and go driving as opposed to cruising on the interstate for 200 miles will give you different mileage results over the same distance. Also, ethanol blends in the fuel will vary, but in Idaho we could buy premium gas with NO Ethanol and got great fuel mileage. "I'm just sayin'"

Rono

  Ron Lane,  Meridian, ID

It's true that all of the pumps at normal stations here in NC have 10% ethanol. You have to go out of your way for pure gas.

My car has a lot of surface rust that has been painted over. The hood, roof, trunk, and fenders have a coarse texture, like 60 grit sandpaper but not as sharp. I'm sure that doesn't help with aerodynamics, but do you think it could hurt to the tune of 3-5 highway mpg?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

my story have 272 with g heads in 56 crown 3 speed overdrive. engine has protronix spark autolite carb with 1 inch spacer timing set 10 degrees plugs are ngk split vtips steel wires. always use 10% gas.mpg is always around 20. this year went on 700 mile trip first tank got 22 mpg. just made another car with 292 with the same setup. car has auto trans. will let you know what it does.

If you’re not checking the actual content of ethanol in the fuel, then you really don’t know what’s there.  The gas pumps typically say ‘May contain up to 10% Ethanol’ meaning it does not have to be there at all to meet that criteria.  Premium fuel typically is maxed at 5% ethanol while you will find the 10% amount in the 87 and 89 octane grades.  I do check the fuel content regularly here at the shop simply due to dynoing a number of engines on pump gas.  An engine ran this last Tuesday found that the customers supplied Valero fuel had 3½% ethanol rather than the normal 5% so unless you check, you simply don’t know.  Up to 30% ethanol has been found in fuel that’s been checked here and there are a variety of reasons that can help to explain how the ethanol content can get that high.  That 30% fuel obviously didn’t run well and once the percent content was recognized as the problem, the fuel was simply changed out for a 5% blend and all was well.

Lorena, Texas (South of Waco)