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By peeeot - Last Year
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I've put 3300 miles on my Crestline since purchase. I have tracked every fill-up and my overall average is 15.3 miles per gallon. My odometer is GPS-verified to be accurate, so I believe this is real and honest fuel economy. The past several tanks have all been almost exclusively highway miles (commuting to work around 65-70 MPH). With overdrive, my tach is reading a little under 2500 rpm at this speed. Economy on these tanks has been 15-16 MPG. Worst tank I have ever recorded was 13.93, best 19.24 (once--thinking may not have filled the tank as full as usual).
Does this sound about right?
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By 55blacktie - Last Year
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I'm wondering about 2500 rpm at 65/w overdrive. What is your axle ratio? Is your 312 stock? Of course, the overdrive will not help your town mpg.
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By FORD DEARBORN - Last Year
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Yes, this sounds about right. I am in that ball park too. 15 to 17 mpg if I drive normally. 1964 F100 312 mild cam, 3.5 rear end T5 trans and fairly large diameter tires. My engine turns about 2100 rpm at 70mph. I bet if we could burn fuel as it was in the day, our mileage would be at least 2 mpg better. But does it get any better than driving behind a fine running Ford Y-block?
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By peeeot - Last Year
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Axle is a 3.9 ratio and the 312 is stock. It’s a bit tired but runs really well. According to my calculations, given my tire size, 70 mph should come in at 2370 rpm, and that seems about right for what I see on the tach.
I’m thinking the car could do upper teens to 20 if I was driving around 45-55 mph without stop-and-go.
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By 55blacktie - Last Year
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2370 at 70 sounds better. I think your mileage is in the ballpark.
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By DryLakesRacer - Last Year
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292. Stock. 2.74 gear. Cruise-O-Matic. 27” tire. 12 mpg over 11 years of city driving. Can get 13.5 on hyway, but it’s always combo.
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By 55blacktie - Last Year
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DLR, unless you've got the "pedal to the metal" on the highway, your mileage concerns me. I would check your air:fuel ratio.
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By DryLakesRacer - Last Year
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Always been that. Even with single stock 4 barrel. Dual quads,Carter WCFB’s, made no difference. I drive with a very light foot. Automatics with the heavy converter we’re always as bad even in the 50-60’s with stop and go like 99% of mine is. Exhaust is very clean. Thru bumper exhaust tips are never black or sooty..ever. I’m not going to add a bung for an analyzer. I’ve never driven a full tank out on the hyway. I also keep a log on every tank fill up which is usually every 3 months.
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By MoonShadow - Last Year
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I've been getting high 17's at 70 MPH with my Ted Eaton 325 CUI Y-block and a 4-71 blower! Of course I'm sure the 3:72 gear and AOD are a big part of that. Longest run was from Ohio to New Hampshire and it was 17.9. Love that extra gear in the AOD.
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By peeeot - Last Year
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Moonshadow, is your odometer accuracy verified? My first two tanks were over 17 MPG but that was with a 20-tooth gear. It was optimistic. I have a 22-tooth now and its within 1% of GPS every time.
Do you know you carburetor, jetting, and cruise spark advance? Just curious!
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By 55blacktie - Last Year
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The rotational mass of a torque converter and flex plate/ring gear is greater than a flywheel, clutch plate, and disc? I suppose, if you have an aluminum flywheel.
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By paul2748 - Last Year
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My last longer trip that I took with my 54 ( warmed over 312, 4 sp, 3.50 rear) I got 17 MPG. This was a trip of over 900 miles, most highway but some city. I generally don't compute MPG around local.
TBird was less, last big trip was 6300 miles, overall I got 14. A lot of highway, 65 -70 MPH. Stock 312. C-4, stock 3.31 rear. Included a ride up Mt Hood in Oregon.
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By 55blacktie - Last Year
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Paul, isn't the Tbird a couple hundred pounds lighter? Were you driving with the top down?
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By paul2748 - Last Year
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I'm sure it is. Really can't account for the difference. But there was more stop and go on the longer trip as we stopped at a number of tourist places on the way out and back, including a stop for Hot August Nights in Reno on the way back
.55blacktie (2/5/2023)
Paul, isn't the Tbird a couple hundred pounds lighter? Were you driving with the top down?
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By slumlord444 - Last Year
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My 57 T Bird weighs 3,600 pounds. I’m thinking that the 54 would weigh a little less. Best I got with it is 17 mpg on an economy run. Worse was 9 mpg around town with my foot in it. Was running factory E setup with 3.89 gear and 3 speed stick.
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By 55blacktie - Last Year
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Slumlord, how did you weigh your Tbird? I've not seen any specs that confirm 3600 lbs. Overdrive?
A quick search for 57 Tbird weight shows a low of 2980 and a high of 3350. Does your 3600 include the driver's weight?
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By MoonShadow - Last Year
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I've confirmed my mileage with GPS and its pretty close to accurate. The 3:72 rear was a factory option for police cars soo the gear should be close. I can't tell you about the engine settings. Ted did that on his dyno and I haven't changed it since. He may still have the info. I was quite pleasently surprised by the mileage but the AOD transmission throws a curve in the numbers too.
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By 55blacktie - Last Year
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MoonShadow, the AOD OD ratio of .67 gives you a final drive ratio of 2.49 (not factoring in tire diameter). Although this is numerically lower than DLR's 2.74, your engine is far from stock. Based on posted numbers, I can only conclude that his mpg could/should be better. Did you retain the AOD lockup converter? Without lockup, a big cam could be a problem at low rpm highway cruising speeds. Apparently, in your case, the weight of the torque converter is not an issue as far as your mpg is concerned. However, this does make me wonder if DLR's torque converter could be slipping at lower rpm.
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By MoonShadow - Last Year
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I used a 2500 stall converter so no lockup. I certainly didn't expect that type of mileage until I had to drive the car home from the Y-block nationals. My tow van lost an engine so I left it and the trailer behind for repair. A pleasant surprise! The overdrive automatics do wonders for fuel mileage. I've asked a transmission company it I can swap in one of the 5 or 6 speeds with the AOD adapter. They say those will replace an AOD in a normal application.
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By slumlord444 - Last Year
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I’ve weighed its several times over the years at my local grain elevator and at the drag strip. The 57 Custom 300 I had in the late 60s was about 3600 pounds with a 390 and 3 speed. I’ve found that factory advertised weight is usually less than real world weights.
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By ian57tbird - Last Year
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When a car here is registered for the first time from another country, it has to go over the weigh bridge.
My TBird came in on the nose at 1.6 Ton with about a 1/4 of a tank of fuel. All cast-iron 312 with auto and porthole top.
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By 55blacktie - Last Year
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That's 3200 lbs.
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By ian57tbird - Last Year
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Sorry my mistake. That was 1.6 Tonne for the TBird. 3527 pounds.
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By BKernell - Last Year
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I have a 450 Quick Fuel on my 292 with a 700R4,I drive it everyday and have put about 30,000 miles on it the last 2 years and it gets anywhere from 15 to 18 mpg 70 mph@ 2100 RPMs
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By peeeot - Last Year
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I recently swapped in an edelbrock 1405 carburetor on a 4-hole spacer with 7547 rods (instead of the 7047 it had originally). This is an old, used carburetor in good condition—not new. Average MPG for the two tanks since I bolted it on is 16.98, driving the same route and speeds as I usually do. Engine feels noticeably more lively/responsive as well. That is a 10% increase in economy over the previous norm!
I went through the 1957-vintage ECZ 4100 with a fine-toothed comb, but neither it nor the 1957-vintage AFB can touch this edelbrock for drivability or economy it seems. I guess that’s what a few decades of carburetor engineering can do for you.
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By harleyjohn45 - Last Year
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When I bought my old Fairlane, 292 Ford o matic, I asked the seller if it would get 14 mpg and he laughed and said if you are lucky. I agree with him it will not get 14 mpg, but I don't drive it a lot and most of my driving is in town. I don't calculate mpg and I also run premium fuel. I call it a gas hog.
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By harleyjohn45 - Last Year
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I also have a couple more old cars, a 57 Belair with a 400 small block modified with a 5 speed TREMEC. It's a gas hog The other is a 30 Ford Hi Boy with a 53 239 Flattie, three speed with a 330 rear and it's also a gas hog. My daily driver is a 16 Lincoln 3.5 liter twin Turbo. It has 365 HP and gets really great mileage. My worst offender of fuel mileage is a 1993 F350 dump truck with a 351 Windsor, AOD and a 456 rear. Some where around 8 mpg.
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By harleyjohn45 - Last Year
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I did not mean Scruby, I meant another brand, it's a beautiful car.
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By peeeot - Last Year
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I had a ‘59 Galaxie with a 292 2-bbl and 2-speed Fordomatic (aluminum case), 3.10 axle, and it would get 14-15 mpg, assuming the odometer was accurate. Thirsty by modern standards but still as good as or better than most pickup trucks that everyone seems to drive these days.
My last tank in the ‘54 was 18.3 mpg. I’m going to try some different rods/jets and see if I can crack 20.
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