whats your average gas mileage?
- Thread starter BeatersRus
- Start date
LocuMob
Fluid Technician with a hat
I didn't realize I burned as much fuel as I did. I happened to run out of fuel and looked at the milage I had driven, then divided that by the gallons I thought it had, giving me a better MPG number. I know that's not the proper way, just figured I had a full tank, drove x miles divided by y gallons = MPG.
1977 Chrysler Town & Country always kept in good tune. Specs:
T code 440 thermoquad dual exhaust, 727, 2.76 open diff. De lean burned using ECM dist and wiring from 74 Imperial (done before the Mopar kit was out there...or at least before I knew about it).
Weight 5050 lbs (3 seat wagon).
Mileage Hwy: best recorded-19.1 mpg routinely get in the 18s.
City: best recorded-13 mpg routinely get in the 11s.
This is the best mpg C body I've ever owned. I honestly don't know why it does so well.
T code 440 thermoquad dual exhaust, 727, 2.76 open diff. De lean burned using ECM dist and wiring from 74 Imperial (done before the Mopar kit was out there...or at least before I knew about it).
Weight 5050 lbs (3 seat wagon).
Mileage Hwy: best recorded-19.1 mpg routinely get in the 18s.
City: best recorded-13 mpg routinely get in the 11s.
This is the best mpg C body I've ever owned. I honestly don't know why it does so well.
twostick
Senior Member
If concerned with driving techniques to get better mileage get one of the old economy/performance Chrysler gauges. Or I guess the same as a vacuum gauge isn't it??. I have a gauge set I will install and I will have a water temp,oil psi and a vacuum gauge cause I always wanted one lol.
A few years ago I was having carb issues with my '75 Imperial and I took it to go see a movie with some friends. We left town with a full tank of gas and drove about 30 miles to the movie theater and then came back (so about 60-70 miles round trip). When I returned home I only had a half tank of gas left! My mileage came out to just under 6 mpg. LOL. Not long after that I had the carb gone through and tuned by a local lifelong Mopar guy.
Typically though I don't check what I'm getting for mileage. Doesn't matter that much what it is, I'm still going to drive it anyway.
Typically though I don't check what I'm getting for mileage. Doesn't matter that much what it is, I'm still going to drive it anyway.
LocuMob
Fluid Technician with a hat
This is my exact thoughts. I just get curious sometimes.
Every Thermoquad I've ever gotten was screwed up/broken.
I really am not concerned either with gas mileage when I drive the Big Boned Gal. I wanted a vacuum gauge really to tell me if the tune was off or a vacuum leak. I drive a 2004 Toyota Tundra crew cab that doesn't get much better mileage with a 4.7 ,32 valve fuel injected V8.
Thanks for the specs information. Other than the really deep gear ratios, there's LOTS of hydrocarbons going out that aren't really contributing to moving the car efficiently. The one T&C seems a tad high, but MORE like it should get. Obviously, gas money is easy to come by for some of y'all, but if the mpg increased by 15% or more, that's more disposable income for other things, even car parts. It used to be that a good Chrysler would get about 16+ mpg on the road, if it didn't, something was wrong somewhere.
In the middle to later 1970s, we sold a good number of Chevy 454 pickups, 3/4 and 1 tons. So many of them never got more than about 8mpg running down the road empty. We generally put 4.10 gears with them as people wanted them "to work and pull". Later, I found out that similar Ford F250s were similar.
Admittedly, where you drive and how affects mileage a good bit. PLUS how much time is spent with the engine idling (for whatever reason).
Still, though, IF the carbs are calibrated for a cruise mixture of 14.2 to 1 air/fuel ratio, mpg should be much better. Regardless of the mph/1000 rpm of the vehicle, that a/f ratio (with ethanol gas), which is optimal for E10, it still sounds like a big lot of inefficiency or a too-rich mixture is happening. The factory vehicles will run a 14.8 to 1 a/f ratio, which is optimum. The factory ELB engines would do more like 18.0 to 1m but needed the electronics to make it work well. Are the spark plug insulators burning "bone white" after cruise or are they darker and sootier? Whether it's a richer carb calibration and/or a strictly mechanical advance distributor (even with a fast curve), there's some inefficiency in there, somewhere.
As for driving style, the old "barefoot with an egg between your foot and the accel pedal" isn't the best fuel economy tactic. Brisk acceleration to cruising speed gets you there and into the most economical cruise economy mode quicker. Accelerating very slowly, staying in the lower gears longer, is not the best way. On every car I've rented (since the mid-1990s) that's had an "Instant Fuel Economy" readout, I've always watched that as I drove. Neat thing about fuel injection is that in "coast" mode, the fuel delivery is trimmed back greatly, yielding 99mpg on the Instant Fuel Economy readout. Carbs don't do that.
On many of y'alls modified cars, I could see 12-13 on the highway, even with the lower gears, but 8-10 strikes me as "there's something wrong somewhere", even if it starts and runs easily. Of course, I'm talking about steady-state high cruise at 60-70mph. The deeper gears might mean the engine is turning 3000rpm, which should be right in the meat of the torque curve with cylinder filling being more optimum, along with engine efficiency . . . unless the engine is calibrated with too-rich mixtures in non-power cruise situations.
In the later 1970s, each year Chrysler (along with other manufacturers) published books with listings of their vehicles' EPA mileage ratings. In the Chrysler books, they had information on driving for best economy AND charts of how much thing like axle ratio change would affect fuel economy. Some great engineering information of how efficient and EPA compliant Chrysler vehicles were . . . including the B/RB cars.
ONE thing I've found is that Chrysler set the transmissions to upshift too soon at part throttle. I'd always thought our '66 Chrysler did good, but when I went to a west Texas city, it more like a drag race at each red light. I started to manually shift just to keep up. I ended up adding 2 more turns preload on the kickdown rod to raise the shift points in "D". That worked well! The adjustment was later a sliding interface on the '70 Monaco and the '72 Newport. On my '80 Newport, the adjustment is hidden under the floor pan, so I got a small black wire tie and put it in the end of the slot of the kickdown rod, so that the carb pin contacted the wire tie, effectively adding more preload to the adjustment. Raised the shifts points just right. More acceleration with less throttle input, keeping the carb out of the power mixture.
Now, for another point of reference. My work vehicles are Chevy pickups, 1/2 tons through the years. The '76 I had was a 250 six cylinder with 3-speed manual, 3.73 rear gears, and L78R-15 tires. Always got 14mpg in a mix of mainly freeway driving with a little surface streets. The '78 C10 was a 350 4bbl, 3.42 gear, P235/75R-15 tires. Best it ever did was 13.25mpg on its second full tank of gas. From there it went to about 11 and stayed there, no matter what. But when we got the first throttle body injected V-8s in '87 people raved about how much better they ran, but complained about the fuel economy at the first oil change. LOL On fuel injection, the fuel is added as you move the accel pedal downward, but on a carb, when you move the throttle, it takes additional air flow to pull the fuel from the float bowl into the engine. I was asked to log my mileage and I did. It was a 350 TBI with 3.08 rear gears and P235/75R-15 tires. Speed limit was 55mph, although I sometimes went p to 60. Using the old fuel economy driving tips, I was able to log many tanks at 20mpg average, using the cruise control. Considering how thirsty prior pickups had been, this was a fuel sipper! Better than the 305 4bbls of the middle 1980s with 2.56 and P235/75R-15 tires. At the present time, I've got a 2014 GMC Sierra with the LS 4.3L V-6. In MDS, it goes into V4 mode as it's a 90 degree V-6. In the same driving orientation, it generally gets 20.6 mpg with a cumulative total of 19.9mpg for over 10K miles. It's now got about 145K miles on it. Now, when I spend a good while with it idling with the a/c on, the average mpg drops to about 15mpg on the trip computer. By the way, I do work for a GM dealer, which has supported my Chrysler "habit" nicely for the past 40 years.
One truck I had was a G2500 box van. Gearing was such that it ran 1700rpm @ 70mpg in OD. With the stock Bridgestones and a 70mph speed limit, it would average a best of 13.8 mpg on strictly highway runs. When the speed limit went to 75mph, it dropped a bit. When they put some deep-treaded Firestones on it, mileage dropped to 11mpg and could never be made to get back up, even with increased inflation pressures. The tires were absorbing too much power and resultantly, fuel, compared to other tires! In the 1990s, one of our salesguys bought an S-10 4.3L V-6 5-speed. As he fancied himself "a hunter", he went down and got some Buckshot Jones Monster Mudder tires. That little V-6 never got past about 14mpg, no matter what. Difference was the bias ply tires and their flexy deep tread lugs. He finally got another truck and an engine that would better pull those flaky tires.
Thanks for the answers and tolerating my amazement at the low mpg figures.
CBODY67
In the middle to later 1970s, we sold a good number of Chevy 454 pickups, 3/4 and 1 tons. So many of them never got more than about 8mpg running down the road empty. We generally put 4.10 gears with them as people wanted them "to work and pull". Later, I found out that similar Ford F250s were similar.
Admittedly, where you drive and how affects mileage a good bit. PLUS how much time is spent with the engine idling (for whatever reason).
Still, though, IF the carbs are calibrated for a cruise mixture of 14.2 to 1 air/fuel ratio, mpg should be much better. Regardless of the mph/1000 rpm of the vehicle, that a/f ratio (with ethanol gas), which is optimal for E10, it still sounds like a big lot of inefficiency or a too-rich mixture is happening. The factory vehicles will run a 14.8 to 1 a/f ratio, which is optimum. The factory ELB engines would do more like 18.0 to 1m but needed the electronics to make it work well. Are the spark plug insulators burning "bone white" after cruise or are they darker and sootier? Whether it's a richer carb calibration and/or a strictly mechanical advance distributor (even with a fast curve), there's some inefficiency in there, somewhere.
As for driving style, the old "barefoot with an egg between your foot and the accel pedal" isn't the best fuel economy tactic. Brisk acceleration to cruising speed gets you there and into the most economical cruise economy mode quicker. Accelerating very slowly, staying in the lower gears longer, is not the best way. On every car I've rented (since the mid-1990s) that's had an "Instant Fuel Economy" readout, I've always watched that as I drove. Neat thing about fuel injection is that in "coast" mode, the fuel delivery is trimmed back greatly, yielding 99mpg on the Instant Fuel Economy readout. Carbs don't do that.
On many of y'alls modified cars, I could see 12-13 on the highway, even with the lower gears, but 8-10 strikes me as "there's something wrong somewhere", even if it starts and runs easily. Of course, I'm talking about steady-state high cruise at 60-70mph. The deeper gears might mean the engine is turning 3000rpm, which should be right in the meat of the torque curve with cylinder filling being more optimum, along with engine efficiency . . . unless the engine is calibrated with too-rich mixtures in non-power cruise situations.
In the later 1970s, each year Chrysler (along with other manufacturers) published books with listings of their vehicles' EPA mileage ratings. In the Chrysler books, they had information on driving for best economy AND charts of how much thing like axle ratio change would affect fuel economy. Some great engineering information of how efficient and EPA compliant Chrysler vehicles were . . . including the B/RB cars.
ONE thing I've found is that Chrysler set the transmissions to upshift too soon at part throttle. I'd always thought our '66 Chrysler did good, but when I went to a west Texas city, it more like a drag race at each red light. I started to manually shift just to keep up. I ended up adding 2 more turns preload on the kickdown rod to raise the shift points in "D". That worked well! The adjustment was later a sliding interface on the '70 Monaco and the '72 Newport. On my '80 Newport, the adjustment is hidden under the floor pan, so I got a small black wire tie and put it in the end of the slot of the kickdown rod, so that the carb pin contacted the wire tie, effectively adding more preload to the adjustment. Raised the shifts points just right. More acceleration with less throttle input, keeping the carb out of the power mixture.
Now, for another point of reference. My work vehicles are Chevy pickups, 1/2 tons through the years. The '76 I had was a 250 six cylinder with 3-speed manual, 3.73 rear gears, and L78R-15 tires. Always got 14mpg in a mix of mainly freeway driving with a little surface streets. The '78 C10 was a 350 4bbl, 3.42 gear, P235/75R-15 tires. Best it ever did was 13.25mpg on its second full tank of gas. From there it went to about 11 and stayed there, no matter what. But when we got the first throttle body injected V-8s in '87 people raved about how much better they ran, but complained about the fuel economy at the first oil change. LOL On fuel injection, the fuel is added as you move the accel pedal downward, but on a carb, when you move the throttle, it takes additional air flow to pull the fuel from the float bowl into the engine. I was asked to log my mileage and I did. It was a 350 TBI with 3.08 rear gears and P235/75R-15 tires. Speed limit was 55mph, although I sometimes went p to 60. Using the old fuel economy driving tips, I was able to log many tanks at 20mpg average, using the cruise control. Considering how thirsty prior pickups had been, this was a fuel sipper! Better than the 305 4bbls of the middle 1980s with 2.56 and P235/75R-15 tires. At the present time, I've got a 2014 GMC Sierra with the LS 4.3L V-6. In MDS, it goes into V4 mode as it's a 90 degree V-6. In the same driving orientation, it generally gets 20.6 mpg with a cumulative total of 19.9mpg for over 10K miles. It's now got about 145K miles on it. Now, when I spend a good while with it idling with the a/c on, the average mpg drops to about 15mpg on the trip computer. By the way, I do work for a GM dealer, which has supported my Chrysler "habit" nicely for the past 40 years.
One truck I had was a G2500 box van. Gearing was such that it ran 1700rpm @ 70mpg in OD. With the stock Bridgestones and a 70mph speed limit, it would average a best of 13.8 mpg on strictly highway runs. When the speed limit went to 75mph, it dropped a bit. When they put some deep-treaded Firestones on it, mileage dropped to 11mpg and could never be made to get back up, even with increased inflation pressures. The tires were absorbing too much power and resultantly, fuel, compared to other tires! In the 1990s, one of our salesguys bought an S-10 4.3L V-6 5-speed. As he fancied himself "a hunter", he went down and got some Buckshot Jones Monster Mudder tires. That little V-6 never got past about 14mpg, no matter what. Difference was the bias ply tires and their flexy deep tread lugs. He finally got another truck and an engine that would better pull those flaky tires.
Thanks for the answers and tolerating my amazement at the low mpg figures.
CBODY67
Thank you for the background info, I suspected you were engaged somewhere in the industry. I will be sure to bug you when my DD 99 'burb puzzles me (unlikely, bought because it's simple and mostly cheap to keep on the road)
The factory numbers you are quoting have been known to be a bit skewed, but maybe more so as CAFE standards came into play. I generally do not track my fuel economy, the last time I did do so in a consistent way was back when the E10 thing was picking up traction. The 'burb did a best of 16+MPG in my normal driving, and about 14 MPG after the switch to E10. I hate hyperdriving and I change nothing in my pursuit of fuel economy. I judge my tire pressures with a tread depth gauge.
I do admit, I want to spend more time playing around with the old cars than I have found the ability to. The Imperials do better than the parts car, but I haven't tracked mileage for a number. My last full highway trip was in the parts car coming back from Carlisle last year... I am guesstimating just shy of 10 MPG, but I was also pulling a small uhaul trailer... I was curious about the mileage, but missed a couple of receipts in my tracking.
commando1
Old Man with a Hat
Joey, you are going to have to steal some bandwidth from your other sites and allocate it FCBO, now... 
And Jeff has a new BFF...
And Jeff has a new BFF...
Ripinator
Old Man with a Hat
Also, if yer traveling with wimmen, factor in a 30% longer travel time. . .
commando1
Old Man with a Hat
And old men in hats with BPH....
Ripinator
Old Man with a Hat
With that tall gear and all, I would think you could do better than 12 mpg. During the last century, I had a '66 Plymouth Belvedere II with the street hemi engine, four-speed and a 3.55 rear gear. We took a trip to Chambersburg, PA, and on the way back, I decided to keep my foot out of the other six barrels of the two four-barrel carbs. I got 17.5 mpg on that trip. Of course I was running Sunoco 260 (106 octane, I think) - not the crappy gas we hafta put up with today. . .
Dads300
Member
I haven't DD'd an old car in about 14 years. The last one was a 67 Barracuda that I drove daily for 10 years. The final iteration was a late 70s 360 w/eddy 650 carb, o/d 833, and 3.23 gears. Back and forth to work with that combo was solidly 18 mpg, sometimes in the high 19 area. I had the carb and ignition dialed in nicely, and the o/d let me cruise 75-80 with traffic on the freeway. That was a pretty nice little combo. Just before I let that car go, I took my 71 d100, stock 2bbl single exh 318/np445, 2.76, p235/75r15 tired longbed 2wd to leave at my father-in-laws house in Idaho. Travelling I-80 from Sacramento to southeastern Idaho at 75 mph, that truck averaged right at 15 mpg for the entire 750 miles.
If parts have been swapped over the years, old cars can really need some tinkering to make run correctly. Even if they start and run acceptably, they can stand some fine tuning to optimize the combination.
Travis..
If parts have been swapped over the years, old cars can really need some tinkering to make run correctly. Even if they start and run acceptably, they can stand some fine tuning to optimize the combination.
Travis..
Jeff earned the old man with a hat status on his first post.....
'70 Newport 440, 2.76 gears: best I've ever had was 15, fully loaded, 4 people, top up and AC on. Average on highway 12-13. I got 13.3 a year ago on a 300+ mile trip up the mountains and back. Around town average is 8.
My '62 New Yorker with 413 and 2.93 rear was 18 on the highway. Thought that was excellent. Incidentally, that's what they got in '62 when they won the Mileage Award for Luxury cars.
'79 Cordoba, 360 4bbl, 2.73 gears: 16-18 highway.
'93 Dodge B250 Van, 318 Magnum, 2.91 gears: 18-20 highway. That was a GREAT vehicle!
'87 Ramcharger, 360 4bbl, 4-speed, 3.21 gears: 12-15 highway.
'17 Durango RT, 5.7 Hemi: have seen 25 MPG three times!! Whoo-hoo!
My '62 New Yorker with 413 and 2.93 rear was 18 on the highway. Thought that was excellent. Incidentally, that's what they got in '62 when they won the Mileage Award for Luxury cars.
'79 Cordoba, 360 4bbl, 2.73 gears: 16-18 highway.
'93 Dodge B250 Van, 318 Magnum, 2.91 gears: 18-20 highway. That was a GREAT vehicle!
'87 Ramcharger, 360 4bbl, 4-speed, 3.21 gears: 12-15 highway.
'17 Durango RT, 5.7 Hemi: have seen 25 MPG three times!! Whoo-hoo!
We've got a 2000 jeep wrangler, straight 6 with a 5spd. I drive it a lot and get between 22-24mpg. My wife drives it and rarely sees above 17mpg. I've ridden with her a lot and she is a bit more aggressive on acceleration and stopping but nothing outrageous. And she's half my size! Between the two of us I would guess my slower acceleration and probably 5mph slower top speeds accounts for most of the difference. But then we have a van that sees the same mileage no matter which one of us is driving... but it's an automatic. She may also idle a lot, which might affect it. Definitely a lot of factors that influence it.
Joey, you are going to have to steal some bandwidth from your other sites and allocate it FCBO, now...
And Jeff has a new BFF...
I was thinking similar thoughts as I got to these elongated posts
rags
Senior Member
0. i'd have to actually drive the cars to get miles per gallon.
