MPG?

[Barabbas]

I was working on the interior of Doris (52 Cranbrook) and found a mileage notebook from 1969.

I was shocked to find that she averaged 22.7 mpg over a 16 month period (12000 miles) with a standard tranny. I remember my the '52 Cambridge that I had in High School got about 17mpg and now Doris with radials and an O/D gets about 18.8. Now part of the difference is that in 1969 Doris was driven around the cornfields of Des Moines and now she is driven in the foothills of the Olympics but still...22.7 mph? BTW I have calibrated the odometer and it's within 2% of actual. What do you guys get?

[Dodgeb4ya]

You won't get the best mileage with todays low BTU's fuels in a carburated car or truck-especially with winter blends!

[TodFitch]

The driver's style makes a difference. I've measured 10% to 15% difference between two drivers on the same car.

As Dodgeb4ya noted modern gas has lower energy density. Probably worth 10% on mileage there.

And then engine efficiency varies with RPM. Given the gearing on old cars, I'd guess that 30 to 35 MPH would be the sweet spot for that. And the power needed to move the car goes up a lot with speed. So if the car was mostly driven sedately on 30 MPH to 40 MPH roads "back in the day" but you are pushing 50 MPH, 60 MPH or more then there would be maybe 20% or more decrease in mileage.

Add all those up and the 33% difference in mileage you posted is within the realm of reason.

P.S. I've gotten 17.2 MPG over the last couple of years on my 1933 with its stock 190 cu. in. engine, 4.375:1 rear end and 5.50-17 tires. I typically drive 55 MPH or so when going any significant distance. Last October I averaged about 60 on the one day trip to Central California and back (just under 500 miles for the day).

Edited December 1, 2010 by TodFitch

[Barabbas]

okay I've done some googling and it looks like "Back in the day" gas had 125,000 Btu and today's 10% Ethanol blend may have 112,000 so your 10% guess is right on. I expect that my foot is a little heavier than the little old lady from Des Moines, but I'm still impressed that she could get 22.7.

I did do some checking on the Drag Coef and the best estimate I could find for a P23 is .75! (about double that of current cars)--so speed does kill gas mileage for these old girls. I guess I will live with the 18.8, I would much prefer going 60+ than getting increasing my MPG by going 45

[Young Ed]

When I'm with our POC group traveling we go 50-55 and I get just shy of 20mpg. Push the freeway speed to 60-65 and it drops to 16ish.

[daddyo23]

I usually run 60-65 and get 19-20.

[james49ply]

has anyone checked mpg with an overdrive unit?, I just went 1,000 miles and averaged around 17mpg running 60-65 mph.I plan on installing od to get better mileage and save the poor girl from spinning so fast.

[Alshere59]

has anyone checked mpg with an overdrive unit?, I just went 1,000 miles and averaged around 17mpg running 60-65 mph.I plan on installing od to get better mileage and save the poor girl from spinning so fast.

Short trip (90 miles highway) with an R7 over drive average speed 65. Mileage 22.8. Rebuilt Stock 230 bored twenty over head shaved 30 thousandths. Dual carb Fenton with Carter BB's. Rea rend ratio 3.9. 15 inch tires. (To lazy to go get the exact size.) I did have an intermittent miss from a worn distributer shaft. So until I get that back from being rebuilt and my overdrive being looked at I cant try it again. Love getting bugs out after a rebuild.

[JerseyHarold]

I didn't check my MPG's on other '52's I had, but my father's '52 Cambridge got 16-17 city and 22-23 highway in the late fifties and early sixties.

[bbuswell]

I have a T5 with a .76 O/D and 3.45 rear. I drive mostly on the highway and it totally depends on the speed. 60-65 mph I get 17-18 mpg; 75-80 mph I get about 12 mpg...

[hotrodbob]

With my stock worn 218 I got 12 mpg. After the rebuild, .070 over bore, Isky cam,Edmunds head cut .010, block decked .010, Offy intake with two stock carbs, radial tires (235/75x15 rear, 205/70x15 front) set at 32psi, 3 spd and 3:90 rear gears I got 20mpg at 60-65mph. That was before the current crap gas though. Oh and I run Castrol Syntec oil.

Edited December 23, 2010 by hotrodbob
ms spillinz

[james49ply]

Bone stock P15 running 55-65 I average 17MPG:(, plan on OD to get better mileage and lower the RPM's:) if I run 40-45 mph I do get better mileage but not much, maybe 1 0r 2 mpg. here the fuel cost is at $3.00 per gallon (all the snowbirds cause an increase in fuel and groceries:mad:)

[greg g]

If you are planning on the OD to save money on gas, you might want to do a bit of math.

at 3.00 per gallon you will need to drive 6800 miles to recoup the cost of the OD and it installation ( based on 1200 for purchase, restore proper function and wiring and associated parts) the way I drive thats a 3+ year pay off.

If you are doing it for piece of mind regarding your engines percieved greater wear life, go for it.

[Don Coatney]

I have always been a bit dense so can anyone explain this to me.

Burning one gallon of gas produces "X" number of pollutants. For this discussion lets say “X” equals 100. So if a vehicle gets 20 MPG then it produces 100 pollutants per 20 miles driven.

Back in the 70's the government stepped up to the plate and said cars are producing too many pollutants and they mandated smog controls. These smog controls dropped the efficiency of cars so a car that once got 20 MPG now gets 15 MPG. So this car now produces 100 pollutants in 15 miles. If driven 20 miles it now produces 125 pollutants.

Now here we are in the year 2010. The energy efficiency of gasoline has now been dropped an additional 10 percent. This means that when driving 20 miles you will use 10 percent more gasoline

So now with smog controls and lost efficiency driving 20 miles will now produce 137 pollutants if I did the math correctly.

Have we not taken a giant leap backwards?

[TodFitch]

I have always been a bit dense so can anyone explain this to me.

Burning one gallon of gas produces "X" number of pollutants. For this discussion lets say “X” equals 100. So if a vehicle gets 20 MPG then it produces 100 pollutants per 20 miles driven.

Back in the 70's the government stepped up to the plate and said cars are producing too many pollutants and they mandated smog controls. These smog controls dropped the efficiency of cars so a car that once got 20 MPG now gets 15 MPG. So this car now produces 100 pollutants in 15 miles. If driven 20 miles it now produces 125 pollutants.

Now here we are in the year 2010. The energy efficiency of gasoline has now been dropped an additional 10 percent. This means that when driving 20 miles you will use 10 percent more gasoline

So now with smog controls and lost efficiency driving 20 miles will now produce 137 pollutants if I did the math correctly.

Have we not taken a giant leap backwards?

If you are looking at something like total carbon released or total hydrogen released, I think you are correct regarding release per mile being directly related to to MPG.

But if you are looking at things unburned hydrocarbons emitted, ozone or oxides of nitrogen, then the relationship is not as direct. Those pollutants are the product of the combustion process and to reduce them the combustion process may need to be changed in ways that reduce fuel efficiency.

[Tom Skinner]

Way back in another time and place I knew a man named Jim Petrellas, he owned and drove a 1956 Crown Imperial 8 Passenger Sedan. He was in his 50's in the 1970's so he is probably gone now, however, I asked him one day what his gas mileage was. His answer? "My boy Gas is small potatoes" When you drive a large Chrysler Product my question is: Isn't Gas small potatoes?

I drove a 1948 Chrysler Royal with the 250.6 cu. in. six in it then as I do now. I guess us older guys just don't get it? To me gas will always be small potatoes. Particles of unburned Particles? Who Cares? If removing this Thread is Politically Correct then so be it. You'all try to have a Merry Christmas and a Happy New Year here at the Forum. For the Sensitive Crowd - have a happy holiday and save gas while your'e at it every chance you get - so I can drive my Large Chryslers around and have more gas for me.

[TodFitch]

...snip... "My boy Gas is small potatoes" ...snip...

I agree that gas is small potatoes. At least for me in my current circumstances.

In the last 12 months I've spent more on gas for my 1933 Plymouth than I have for my 2004 modern car.

Fuel accounts for a bit less than 17% of the expense of owning and running the cars at my house. I do include depreciation on the new(er) cars as an expense, and depreciation is the largest single expense. Looking at a bigger picture, fuel for the cars is about 3% of our after tax expenses at our house.

[james49ply]

Greg G, I have always been anal about fuel economy, even when gas was $.30 a gallon (10 gallon then = 1 gallon today:(), just something that I have always been concerned with. And I have always said that an engine that has lots of torque is better than lots of HP Being a retired auto/heavy truck mechanic I am concerned about wear, the faster it spins the faster it wears, but to contradict myself, having the engine spin slow causes heavier loads on all moving parts on the crank and pistons. My Harley spins at the near the same rpms as does the Plymouth, and with 165,000 miles:eek:, is running good today. This being said, that unless I could see an appreciable increase in fuel economy I most likely will retain the current original driveline. This tread has educated me as to my future plans, as the cost to change appears to be a tad bit counter-productive.

[greg g]

Back in the day how much of the wear was due to poor filtration, driving on dirt roads, and while our cars were new breathing in particulates from coal burning furnaces and coal powered industry, and even coal burning steam engines. Also diesel belching high particulate exhaust.

Had a duscussion with a fellow who is about 10 years younger than me about snow in the winter growing up, I can remember going out in the morning after an over night snow fall to gleaming white freshly fallen snow, then by the time school was out the snow had accumulated a visible layer of soot from coal and wood fires. He doesn't remember that being the case when he was out and about as a kid. That stuff in the air had to have a impact of shortening engine life back in the day.

[Don Coatney]

Had a duscussion with a fellow who is about 10 years younger than me about snow in the winter growing up, I can remember going out in the morning after an over night snow fall to gleaming white freshly fallen snow, then by the time school was out the snow had accumulated a visible layer of soot from coal and wood fires. He doesn't remember that being the case when he was out and about as a kid. That stuff in the air had to have a impact of shortening engine life back in the day.

In the early 80's I managed coal fired boilers in a food plant. Part of the daily operation of these boilers required using steam to blow the heat exchanger. All of this went up the 125 foot stack. This procedure was always done in the middle of the night under the shroud of darkness. I lived about 1/2 mile from this plant. Particulate from this procedure could be seen in the snow at my house. Per an EPA mandate we had to install an opacity monitor that recorded the ammount of particulate. We were under the legal limit at the time.

[greg g]

Yep and in most cases the "Legal" limit was just a number to point at as a complience measure, rather than anything based on much real science. but the agency and the industry could say they were comlient with the current regulations, thereby ensuring that the industry and the beuracrats could have job security. Love canal outside buffalo might be an example of that type of regulation.

[Robert Horne]

In the early 80's I managed coal fired boilers in a food plant. Part of the daily operation of these boilers required using steam to blow the heat exchanger. All of this went up the 125 foot stack. This procedure was always done in the middle of the night under the shroud of darkness. I lived about 1/2 mile from this plant. Particulate from this procedure could be seen in the snow at my house. Per an EPA mandate we had to install an opacity monitor that recorded the ammount of particulate. We were under the legal limit at the time.

This sounds similar to Cleveland, Ohio a few years ago near the steel mill. Out late on my bike rides in the country, come back to town after midnight, one could see a orange/red fog all over the city.

[Robert Horne]

As for MPG, the 66 Plymouth I had years ago, would go 265 miles on 10 gallons on a trip. It had the 273 V8 with a 3 speed manual trans. The 82 Chevy truck I had would do the same, with a 305, 3 speed manual trans.

[48P15Annie]

All I know is 1/4 on Annie means empty.

Go ahead...ask me how I found THAT one out!

Barabbas, thats a neat little piece of documentation there. I have similar for Annie that was written by the original owner.

[hkestes41]

has anyone checked mpg with an overdrive unit?, I just went 1,000 miles and averaged around 17mpg running 60-65 mph.I plan on installing od to get better mileage and save the poor girl from spinning so fast.

48 Club Coupe, 60 over 218, Offy intake, dual Carter Webbers, cast iron headers, 3.90 gear, R10 OD.

From Plano, TX to Joplin, MO for HAMB drags 2 years in a row. Roughly 870 miles round trip with probably around 100 miles in town driving around Joplin area. First year 19.9 mpg for the round trip and last year 19.5 mpg. Running 60-65 on the Highway - Interstate.

Last year had a front wheel bearing go out on me about 1/2 way home so that may have contributed some to the drop in mpg.