Technical Why Is My MPG So Low?

Hi Folks,

I have a stock 1953 Ford Crestline Victoria with the flathead V8. I have been monitoring my mpg, and I am only averaging about 7 mpg. I recently read where the mpg for my car should be twice that (13-14 mpg). What the heck do you think the problem is?

Caveat: I do have some mechanical skills, but when it comes to automotive, not so much.

Any help would be greatly appreciated!

Jim

 

What condition is the tune on your engine? Is it running good and has good power? Does it miss or bog down? Does the advance in the distributor work? Answers to these questions will give some data to base advice on.

 

What are the driving conditions? mostly around town, short trips, etc?

Does the car feel peppy?

Probably would be a good idea to do a compression test and check dwell and timing.

fwiw I had a couple flathead powered cars that averaged about 9 mpg on long trips...they're not very efficient engines.

 

One I forgot, how are you figuring your fuel mileage? I had a customer once who figured fuel mileage base on the postion of the fuel gauge.

 

I wish mine got 7. Economy is in the eye of the beholder

 

I do what I would consider average trips on mostly backroads, but sometimes on two-lane highways. I average about 20-30 miles per cruise.
The car is anything but “peppy”. So sluggish from a dead stop, even floored! I can’t answer your question about advance. I think that I am starting to hear a possible valve tap.

I divided total miles driven by the number of gallons of gas used to refill the tank.

 

@jaracer My math might not be the best in the world, but I’m using some app that calculates mpg.
Edit: Plus I save all of my gas receipts, so I have a general idea.

 

"I’m using some app that calculates mpg."

what does that even mean?

fill up your tank. note the mileage.
drive the car 50 - 100 miles.
fill up the tank again.
divide the miles driven by how many gallons of gas you burned.

 

...That's the app I've always used.

 

Worry more about the SPG's than the MPG's. (Smiles per gallon over Miles per gallon)

 

A flathead isn’t going to pull your head off but from a stop it should feel nippy. What do the plugs look like? Have you checked the timing.

 

When did you last tune up the car? HRP

 

Sounds like she’s tired
as stated above I would start with a compression check

 

General idea! B crap. The ONLY way to figure mpg is ---- fill that sucker UP. Record the odometer miles. Drive until you want to fill UP again. Starting miles is 49362. Next fill up , odometer reads 49548.. Subtract the first miles, 49362 from the ending miles, 49548 . So you drove, between fill ups a total of 186 mi. Took 12.5 gal to fill up. Divide 12.5 into 186, giving you 14.88 mpg.

Ben

 

Is it an automatic or stick? The difference between the two is 3-5 mpg. If all the cylinders have near stock compression, the carb is working properly, and the loadmatic ignition is operating correctly, and also the choke is off when warm/hot 11-13 is normal for those when new. Today’s gasoline is s**t to say the least and because of the ethanol content does evaporate.
If it’s not peppy” the first place to look is the ignition advance which can be done with a timing light… good luck

 

If it isn't "peppy" enough to get the car moving the way you want, and you mostly drive with the gas pedal floored from most stops, it will never get good gas mileage.

The old flathead will not perform like your modern fuel injected 4 cylinder car when you leave a stop. Your flathead V8 probably doesn't have as much power as your modern 4 cylinder, and the the drive train behind it isn't nearly as efficient as your modern car's drive train. If you are expecting it to be, 7 mpg is probably as good as its going to be.

The best you can do is get it tuned up by some one that knows how to do a tune up on your flathead V8, and learn to enjoy the slow cruise. The next options are to live with the sluggish car, sell the car, or install a modern drive train in your old car. There are reasons people have been replacing the old flathead motors & the transmissions behind them for many years.

 

"Edit: Plus I save all of my gas receipts, so I have a general idea."

gas receipts have nothing to do with gas mileage

 

All of the guys who have posted on this are right on. You say you don't have much automotive experience? Look in the " The Antiquated" classified for either a Ford service manual or a Motors Manual for your year car. The basic information you need is in there. Then, if you have questions, come back here and ask. There is no such thing as a dumb question except for the question that never got asked.

 

tires still stock height?

 

My bus gets that kind of MPG with a 500 caddy

Do the above suggestions

start with a comp test
Go from there

 

Why is an app needed for simple math?

 

Math is not that simple for some people.

 

>>Why is an app needed for simple math? >>>

Cuz it's a smartphone. It automatically uses a GPS for miles & swiped e-receipts for gas used. Then he pushes a mileage button on the app screen. And 7mpg pops up on the screen. The simple modern way. No old school odometer, pencil & paper or simple math needed. You gotta get with the program man!.

 

It sounds like the poor thing needs a good tune up including a compression test and probably a carb rebuild.
Piddle assing around town town at low speeds and having to push down on the pedal to get it to even half way accelerate isn't helping either. A fifty or sixty mile highway trip (55 mph 2 lane is fine) and back would give you a more accurate reading especially if you fill up at the same pump at a newer high volume station and stay from the old ass gas station converted to a mini mart with the 70 year old tanks still in the ground. Costco is normally going to have the cleanest gas around. That according to my brother in law who used to deliver fuel to them and other stations.

 

Used 55 gallons to go almost 400 miles once

 

I do that all the time in my old truck...around town...

 

And that was after adding an overdrive.


The look on folks faces getting passed by a school bus on the interstate was worth it

 

@Yardbirder You haven't told us what transmission you have. Those Fordomatics were not known to be very efficient when in good condition, let alone when they got tons of miles on them. Give us ALL the details....

 

There isn't one solitary thing that anyone needs a smartphone for , other than to share your daily history with everyone & most businesses do that for you !

 

No, we don't need them...but they sure are handy for doing a lot of things.

I still do mileage the old way with a pencil and paper and an abacus. Oh wait...I use the calculator app on the phone for the division, and usually the sums also. Because I always have the phone with me, I don't have to go looking for an abacus (or calculator).