So, with with the summer old car driving season coming up and $4.00 gas on the horizon, I'm curious about what kind of gas mileage people are getting with their flatheads?

The best I can do with my '36 Sixes is about 16 highway, 13-14 around town (which is most of my driving of course). Not much better than a modern SUV, and this from a car touted as the "economy leader" that year.

We don't have much Ethynol here, but I'm guessing mileage is worse with that mix?

Most of the gas I use has 5% ethanol. I drive about a thousand miles a month, half in town and half in the country. I drive the car to keep up with traffic in the city and cruise about 50 to 55mph on the highway. Over all I average about 19 mpg. Before ethanol I averaged about 19 1/2 mpg. The only difference now is that I use NKG sparkplugs and only have to change them every second year rather than every year when I was using AC's and Champions. Are the plugs better or does the ethanol make them last longer. I don't notice any other difference. Highway mileage alone is about 20 to 20 1/2 mpg and city mileage can get down to 16 in bad weather.

Could be a little on the low side. But cars didn't get very good mileage back then.

Smaller cars like Ford, Chev, Plymouth would average about 17 or 18, maybe 20 with a good tuneup.

Heavy models like Cadillac V8, 15 or so.

Gas milage? Mine is lousy, but what you going to do! I'm driving a 1950 4 door Chieftain Delux with an eight and a hydromatic so I do not expect a lot. Runs in the 14 MPG range for me. I do a lots of driving with the car loaded down like a Mack truck, and I'm sure that doesn't help any. On the flip side of the coin, it only got 11 MPG when I first started driving it. Getting the right oil, tune up, tire presure, and all that ther stuff you are supose to do really made a difference. That's like a 25% increase. Lukey

I get 12 MPG on the 48 S8 with automatic Tranny. Have not checked the 46 Standard yet. -Rick

Hi Rick, ouch 12 mpg's gotta hurt with these gas prices. Not driving it to So. Dakota this summer I guess? :-)

I'm envious of some of your numbers. I get about 10 mpg in town and maybe 14 or so on the few times I've had my 49 Streamliner on the highway. It's an 8 with manual transmission. Most of my outings are less than 10 miles, and in my neighborhood there's a stop sign almost every block, so it's probably not a good sampling of what the mileage could be. I still have fun though.

Bill

No, I'm not going to POCI in South Dakota, don't know what criteria they use to choose locations, must be a drag strip out in the middle of nowhere, I'd rather attend the Flathead Reunion in St. Michaels, MD in early September. All pre-1955 Pontiacs and Oaklands, friendly folks who dress in period style and fun non-competetive 40mph activities! See the Early Times Chapter website for details. Thanks. -Rick

I have a '32 6 with rebuilt engine but I am not running my original Marvel carb yet. When cruising around town I seem to get in the 12-14 mpg range. On the road when I am touring I get 15-18 mpg. That is curising in the 45-55 mph range. I am hoping when I rebuild the original Marvel that I may do a bit better.

Try a straight 8 with dual carters maybe 12 mpg on a good day. I do have a progressive linkage I am going to try and it runs very well with fuel in proportion to all the clinders

Today on the I5 cruising at 55-60 mph in 85 degree heat I drove 99.5 miles using 7 gallons of gas. 15 mpg with the original marvel carb. If I drive 50-55 I get about 18 and on a really good day driving 50 mph steady 20mph is the bst I can do.

My 48 convertible,straight 8, manual trans, has been as far south as Savanna, Ga. I live in central Ohio. The old girl runs a steady 15 mpg @ 55 mph. I wont keep up with traffic, the engine really screams at 70 mph. I think she would do better if I could get those 4:11 gears out and replaced with a better ratio.

4:11 was the high end ration in '36. I'm planning on switching out my mid-range 4:44 a 4:11 set in hopes of improving my mileage.

Speaking of gas...what advice does someone have as to an additive I should be using on an original setup 8 cylinder 1950 Chief? I imagine I should use the highest octane gas avail but do I or should I use an additive for further octane or lead?

Also, what about oil? What kind of oil weight do you suggest for the same setup, approx 96k miles?

I have a 1950 Chieftain 2 door sedan delux, straight six and I have been averaging around 10-11 mpg as best I can tell. I have been pushing it more >60 mph to see what she can do.

Seems like I should be getting better gas mileage, especially for a six. I typically use 89-93 octane and I a 20w 50 oil and I occasionally add the "mystery oil" additive to a tank.

Others seem to be getting better mileage with larger engines. It starts to get very expenses even just cruising around. Any suggestions would be appreciated!

Thanks,

Christopher

We took our '53 Chieftain to Virginia at the end of May for a Pontiac show and averaged 16.5 mpg for the 1,250 mile trip. It has the straight eight and Hydra-Matic and we kept our speed to an indicated 55-60 mph; (53-58 actual) I use regular unleaded, (87 octane) and Pennzoil 20W-20 in the crankcase. The car is tuned to factory specification plus I've got the octane selector advanced 2 degrees. I don't believe the engine has been overhauled as it does use some oil, especially when we drove through the mountains. It used 3 quarts of oil for the trip. I usually get nearly 600 miles to the quart around north central Ohio where its nice and flat.

Those numbers from previous posts are really terrible. Old technology cannot be changed, but we still use the same formulas, IE: horsepower:weight. 1950's cars are very heavy, tend to use small engines (by today's standards), and high rearend gear ratios (4.11:1? C'mon). The diff in gas mileage between a six & eight and city vs highway was small.

How is it that my '90 Mustang (cast iron 289 w/AOD) gets 17/25-MPG? Sure it's light, but wayyyyyy over powered by at least 100 HP. Is it the EFI? Gear ratio (2.7:1)? Radial tires? 10W-30 oil? Maybe it's the whole package wrapped into one.

From our hotrod days, we learned about diminishing returns, and a beneficial compromise: Why install a six when an eight uses just as much gas, but produces more ponies?
Rather than change your classic into something it wasn't, learn to enjoy your car for its originality. The price of gas and oil in the 1950's was a non-issue. At 4 Gal/buck, you could fill the tank for $4-5.

Let's count our blessings. Owning classic cars is extravagant but rewarding. As a hobby, it's costly, all the way around. Few families can afford that with the rising prices of everything.