Pre computer era high mpg cars

[shovel]

I owned a '73 Duster - not the "Feather" duster but it had a 225 /6 with an RV cam that the previous owner had installed "for more bottom end", he said. It had a 3 speed auto and cruised at 30mpg any time I was on the highway - seriously not bad for a vehicle that size/era.

Also had an 81 Escort (4 speed manual) and an 81 Plymouth Champ (4 speed manual, but with a 2-range overdrive) - both returned 45+ mpg on highway trips, I didn't spend much effort calculating mpg around town. I didn't spend much effort calculating mpg at all, really, but when the gas gauge broke on the Escort I compensated by watching the odometer, 450 miles meant I was close to empty and needed to put another 10-12 gallons in.

[drainoil]

Originally Posted by shovel

I owned a '73 Duster - not the "Feather" duster but it had a 225 /6 with an RV cam that the previous owner had installed "for more bottom end", he said. It had a 3 speed auto and cruised at 30mpg any time I was on the highway - seriously not bad for a vehicle that size/era.

For a car of that size to pull that kind of hwy mpg well before computerization and fuel injection became common is saying something imo

[user removed]

Compare Old and New MPG Estimates

Sentra Diesel, original EPA 48 combined.

regards
Mech

[shovel]

Originally Posted by drainoil

For a car of that size to pull that kind of hwy mpg well before computerization and fuel injection became common is saying something imo

Indeed! I was 22 when I owned it, and that was more than a decade ago - I was interested in fuel efficiency for purely monetary reasons at the time - not as much for curiosity or hobby reasons - so I wasn't paying the strictest attention to what made it efficient. Thinking back, I know it had a 2.xx:1 rear axle ratio, and in general the engine operated at very low speeds all the time, even under heavy throttle kick-downs from 3rd gear into 2nd gear, I don't think it saw the high side of 3000rpm. There was no tachometer, I can only guess at speeds. Idle was very low, and as close to silent as a machine with a carburetor and a nearly open induction system can be - just had that offset "snorkus" thing on a round air filter like most cars of that era.

The car was also quiet on the highway, windows up or down. I haven't been able to find data online for that era's drag coefficient unfortunately but it wouldn't surprise me if it was somewhere in the low 30's despite being rwd and having no attention paid to the underside aero.

Thinking of that era's fuel sippers, dad had an I6-powered 74 Maverick 4door when I was young, and I remember we always took that vehicle on road trips because he said it got much better fuel mileage than the other 3 vehicles we owned (super beetle, pinto, chevy scottsdale pickup I6) - also the most comfortable of the cars.

[drainoil]

Originally Posted by shovel

Indeed! I was 22 when I owned it, and that was more than a decade ago - I was interested in fuel efficiency for purely monetary reasons at the time - not as much for curiosity or hobby reasons - so I wasn't paying the strictest attention to what made it efficient. Thinking back, I know it had a 2.xx:1 rear axle ratio, and in general the engine operated at very low speeds all the time, even under heavy throttle kick-downs from 3rd gear into 2nd gear, I don't think it saw the high side of 3000rpm. There was no tachometer, I can only guess at speeds. Idle was very low, and as close to silent as a machine with a carburetor and a nearly open induction system can be - just had that offset "snorkus" thing on a round air filter like most cars of that era.

The car was also quiet on the highway, windows up or down. I haven't been able to find data online for that era's drag coefficient unfortunately but it wouldn't surprise me if it was somewhere in the low 30's despite being rwd and having no attention paid to the underside aero.

Thinking of that era's fuel sippers, dad had an I6-powered 74 Maverick 4door when I was young, and I remember we always took that vehicle on road trips because he said it got much better fuel mileage than the other 3 vehicles we owned (super beetle, pinto, chevy scottsdale pickup I6) - also the most comfortable of the cars.

I do miss my old '74 Dart I had in high school. It was factory gold paint but we spray painted it navy blue in my dads old garage along with my buddy who had a same year Duster. I had many memories in that car even took my first date out in it

That car was so simple to work on mechanically speaking compared to almost everything else I've ever owned. I could also fit 5 of my buddies in it. I think mine didn't get really good mileage as it had really high miles, wasn't taken care of very well by its previous owners, and the carb was very finnicky and needed a good rebuild which at the time I didn't have the money for.

[Frank Lee]

data online for that era's drag coefficient unfortunately but it wouldn't surprise me if it was somewhere in the low 30's

It would surprise the helloutta me. Probably low 40's Cd; high 30's at best.

Thinking about that "36mpg"- it's probably a typo- 26 sounds reasonable/attainable.

[drainoil]

Originally Posted by Frank Lee

Thinking about that "36mpg"- it's probably a typo- 26 sounds reasonable/attainable.

If your talking about the Feather Duster/Dart Lite that indeed was the EPA hwy rating for it. That particular model was available for the '76 model year only.

I agree 36 mpg sounds ambitious and its likely very few got that but even upper 20s/low 30s is still pretty good on 1970s technology considering many newer and smaller cars aren't rated much better.

New Dart Lite Competes For Compact Economy Crown

Funny that back then this was considered by some to be a compact car lol.

Spirit of 76 Dart Lite — CLUNKBUCKET

Dodge Dart - Wikipedia, the free encyclopedia

Dart Lite

In response to increased interest in fuel economy, Dodge offered the "Dart Lite" fuel economy package which weighed at least 150 lb (68 kg) less than the ordinary Dart Sport.[4] The 225 Slant Six was the only available engine, equipped with an aluminum intake manifold for the first time since 1960 and a specially calibrated carburetor and distributor. Bumper reinforcement brackets were aluminum instead of steel, while the hood and trunk lid bracing and inner panels were also aluminum. The Slant Six engine block had already been modified for reduced weight in 1975; in the middle of 1976 production its crankshaft was changed from forged steel to lighter cast iron. The high-flow exhaust system included a dual-biscuit catalytic converter, a 2¼" headpipe, and the muffler used on V8 models. The Dart Lite was equipped with a 2.94:1 rear axle rather than the customary 3.21:1 ratio when the car was ordered with a three- or four-speed manual transmission. The A833OD overdrive 4-speed manual transmission housing was made of aluminum. Like all other Darts, the Dart Lites with automatic transmission came with a 2.76:1 rear axle as standard equipment.[4] The Dart Lite with manual transmission was rated by the EPA at 36 mpg (6.5 l/100km) in highway driving. The Plymouth version was the Feather Duster.

I can't find a supporting link right now but I remember reading in a car rag years ago that Chrysler made an all aluminum block 225 slant six in the early 1960s. It was short lived and were mainly used for performance/racing. I wonder how much economy one could have squeeked out of something like that if built strictly for economy?

And for the extreme eco Duster/Dart enthusiast how about an electric Duster:

MOPAR fan converts Plymouth Duster to electric

[drainoil]

Not trying to sidetrack my own thread but in case anyone cares, here's some supporting info on the aluminum 225 slant six.

Here is a little background and history on the Aluminum Block Slant Six engine

An Exotic Slant Six | Hemmings Motor News

An interesting fact is that a hemi six was made in versions over 300 horsepower (factory) by Chrysler Australia in the 1970s.

Chrysler Hemi-6 Engine - Wikipedia, the free encyclopedia

[slowmover]

The Slant Six just possibly had more FE potential than any other motor -- car or pickup -- into the 1980's. Indestructible was the middle name. As one auto engineer put it, convert it to propane and it'd outlast the sun". With that basis any mods (EFI, turbo) are a good match behind that alu-case 833.