ESP47
Well-Known Member
I'm a little late to the party but I just got a consistent 22.5mpg doing 75mph across the Nevada desert in my 71 Duster super six w/904 and 2.76 gears.
Max MPG- slant vs 318/340
- Thread starter replicaracer43
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Frankie
Member #9641
Did someone mention FI/6?
VSTwister
Well-Known Member
Well I can give you some real numbers as well, but all based on my personal conditions of car, method of driving, etc...
The '79 Dodge St. Regis I used to have had a 318 in it. Automatic, but I can't recall which model. Drove it from about 1991-1993, approx. 60-80k miles on the odometer over that span. It would get about 19-20 MPG at best. Had the electronic ignition, but I don't think it was the "lean burn". Heavy car. It was really slow. I don't know what gears it had but I'm guessing 2:70's.
My '95 Dakota has the 5.2L, with 5 speed trans (5th is OD). 3:55 gears. When I first bought it in 1996, with 18k on the odometer, it would get 16 MPG no matter how hard or light you drove it. The original owner told me that's how it worked for him, and I found it to be true. Enter about 100k+, the motor finally broke in and started giving 18-19 MPG. I did do changes of spark plugs, wires, and general tune-up stuff but not as regular as some of you might. Still driving it today with 247k on it, but it only gets about 14 MPG anymore. Lol. I don't drive it except local, and I mean really short trips, so I know that hurts it. Plus I don't keep up anything for optimal performance anymore. Just fix what breaks to keep it going.
My Scamp w/318/904/2.7X gears I never could give a true MPG on it. I think one time I estimated it to be around 15-16 MPG, but I threw a 4BBL carb on it early on and could never keep my foot out of it when I drive it. Lol.
The '79 Dodge St. Regis I used to have had a 318 in it. Automatic, but I can't recall which model. Drove it from about 1991-1993, approx. 60-80k miles on the odometer over that span. It would get about 19-20 MPG at best. Had the electronic ignition, but I don't think it was the "lean burn". Heavy car. It was really slow. I don't know what gears it had but I'm guessing 2:70's.
My '95 Dakota has the 5.2L, with 5 speed trans (5th is OD). 3:55 gears. When I first bought it in 1996, with 18k on the odometer, it would get 16 MPG no matter how hard or light you drove it. The original owner told me that's how it worked for him, and I found it to be true. Enter about 100k+, the motor finally broke in and started giving 18-19 MPG. I did do changes of spark plugs, wires, and general tune-up stuff but not as regular as some of you might. Still driving it today with 247k on it, but it only gets about 14 MPG anymore. Lol. I don't drive it except local, and I mean really short trips, so I know that hurts it. Plus I don't keep up anything for optimal performance anymore. Just fix what breaks to keep it going.
My Scamp w/318/904/2.7X gears I never could give a true MPG on it. I think one time I estimated it to be around 15-16 MPG, but I threw a 4BBL carb on it early on and could never keep my foot out of it when I drive it. Lol.
A38Valiant
Collector Of Rust
Not sure how relevant it is, but in the late 90s I had a 76 D100 2wd longbed with a slant, 727, and 3.55 9 1/4. Driving well in excess of the speed limit on the 35 mile one way commute I had back then, it got like 12 MPG. Swapped to a 318, 8.4 CR, Hedman hedders, stock 360 4bbl cam, intake, and TQ. Running 80 plus for most of the commute, my mileage IMPROVED by nearly 3 MPG. Oh, yeah, then I could actually load something and still keep up with traffic, unlike the slant.
Can't say how the slants work in a light car, but in a fullsize truck with 3.55s and an auto, there is no reason to ever keep the six.
Can't say how the slants work in a light car, but in a fullsize truck with 3.55s and an auto, there is no reason to ever keep the six.
VSTwister
Well-Known Member
...and that's why I'd have no problem using a 100K mile unit in a street/strip car, even without rebuilding it. Short cab rams, vans, and Dakotas with 100-120K down here are going FOR 8-1200 bucks, complete, running, driving.
moparmat2000
Well-Known Member
VSTwister
Well-Known Member
My Dakota has 247k on it. I've wondered if the heads are cracked. Runs fine though.
motorpirate
serial mopar owner
Bear in mind it takes a given amount of fuel to move a given weight/shape car down the road at a given speed.
I removed the 258 6cyl/5spd from my Wrangler years ago and replaced it with a tune port 305/700R4. it got the EXACT same mileage before and after (16/18 MPG) but sure was a lot faster after!!
I removed the 258 6cyl/5spd from my Wrangler years ago and replaced it with a tune port 305/700R4. it got the EXACT same mileage before and after (16/18 MPG) but sure was a lot faster after!!
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