Average MPG with a 248 c.i.

[414TATA]

I am sure this has been discussed before but I didn't find it with a search.

How many miles per gallon do you get with your 248 c.i. engine? (Just looking for an average)

I am guessing I get about 12 or 13. I have compound carbs. drive about 30% stop & go and 70% highway at 55 - 60 mile per hour.

I could fill up and do the math, but I have never filled the tank and don't trust it to sit full in the garage.

I usually keep only 5 or 6 gallons in the tank. The fuel gauge floats from empty to 1/2 so trying to figure from the gauge is no help

Wayne

1941 Super 51

[egor]

Maybe 12. Single carburetor 38-41.

[60FlatTop]

I think 10-12 should be about right.

Years ago a friend and I went to a distant Cadillac Club meet. One of our local members asked what kind of mileage we got. He said he only got about 12 with his car and others told him they were getting 16-18. At the same time my friend and I said "They are lying to you." A few weeks later we saw him at a local meet. He told us his mileage was a lot better on the way home. We figured the big kids taught him to lie.

Not trusting a tankful of gas in the garage and riding around in public with it full of fumes would not be a discussion to have with the insurance man. Those concerns should be resolved. It is best to remove the tank and check that the bottom, top, and seams are solid. If there is a rubber hose between the sending unit and the steel fuel line it could be deteriorated and someday begin sucking air instead of fuel. That could leave you stranded.

I worked on a '41 Cadillac once. The owner said when he filled it the tank leaked. It turned out that all the rubber on the filler neck connector had crumbled and fallen off. Just the fabric was hanging there. Like running with no cap, the fumes were right there for a passer by with a cigarette.

Bernie

Edited March 18, 2013 by 60FlatTop (see edit history)

[Ben Bruce aka First Born]

Wayne, you will never know until you do a fillup/drive/fillup. But 12 to 14 is about right. Your car probably has a 4.1;1 or 4.4:1 ratio. A '54 or '55 3.36:1 gear set will exchange with yours. But if you only drive a few miles, probably not worth the effort.

Ben

[jeff]

'38 Special, with the 4.4:1 rear gets 12 -14, as noted above. My owner's manual shows a chart with it getting better mpg, but the chart has a disclaimer about perfect conditions, steady speed, etc. On a 300 mile trip of total back roads, I really baby'd it, rarely going above 40 mph. I got close to 16 mpg.

Jeff

[414TATA]

Thanks to all who responded. I think about 12 MPG is going to be it.

Wayne

[FLYER15015]

Wayne,

Being in Fresno, do you get a lot of temp swings/ humidity ?

Up here in Colorado, we get to enjoy all 4 seasons, and the "Baby" sits most of the winter in an unheated garage.

So we keep our tanks full for the winter to minimize condensation in the tank, and of course the recommended amount of "StaBil".

My tank does not have any rubber connector on the fill tube so we don't have to worry about "decay" in that area.

The fuel line is 99% solid with just one rubber connector @ the carb, which we usually replace in the spring, when we wake her up.

Ben,

I'd like to know more about swapping rear end ratio's, especially regarding the '40 series 90 cars (long wheelbase).

Can you switch out the ring and pinion, or do you have to replace the whole torque tube/rear axle ?

I'm not after "milage". Just trying to slow down the "rev's" a bit on our longer trips.

Mike in Colorado

[414TATA]

Mike

This may be a double post answer to you. My first one seems to have gone missing.

A cold winter night here is about +28 F. "Miss Super" is in the garage which usually stays about 50. Summers are HOT there are days when it is 100 in the garage. Humidity is fairly low.

I usually have less than a 1/2 tank of gas and drive her at least once a week.

Wayne

[Buicknutty]

Last year I got about 12-14 MPG on my '41 Roadmaster with the 320 engine and the stock 3.9 ratio, with over 1,000 miles on the rebuilt engine. The upper number was nice easy driving on fairly flat backroads, and not over 50 MPH, the lower number was cruising about 60 MPH on the highway, which I thought was pretty decent mileage, for that car.

I have a 3.4 rear ratio from a '55 Century that I want to swap in this year, mainly to get the revs down a bit at highway speeds, though it will be interesting to see what difference it makes to the fuel usage.

Keith