gas milage range for engine size

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1969dodgedartgt

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Hey guys, I'm wondering what gas mileage you get on your engine, and what range of milage is expected for a given engine size. sure this will depend on what you got going on but whats the expected range?

my 318 gets anywhere from 10-20 mpg depending on lead content of my foot.

Just managed to get >20 mpg today on a gentle highway drive.

what mpg should a 318,340,360,440 get?
what mpg do you get? and what are you driving?

(quick search did not turn up another thread like this....)
 
There are many many MANY factors that affect fuel mileage, and you cannot just pick an engine size

"Back in the day" we had a 389 Pontiac 2 bbl that routinely got over 17, and those were pretty heavy cars

Car weight

Tires, rolling resistance, and the type of roads--if you live down a long stretch of gravel/ dirt/ unimproved road, that is quickly gonna kill your average

Gearing, and I don't just mean taller. There IS a limit, and you can get the engine below the torque range

Engine build, cam, cam timing, ignition advance curve and initial timing, vacuum advance, carburation and jetting, it just goes on and on

Engine temp---engines operating up in the 180-190 range will get better mileage than cooler engines IF the fuel system is up to it (no vapor lock or fuel boilover)

This is just a "few" things and of course the size of the driver's right foot

This just came up over at Moparts and I used my own car "back then" as an example.

My 70 RR, a sixpack car, with a heavy Dana 60 and 3.54 gears, weighed about 3860. I dropped a stock 71 high compression 340 into it, variously with TQ, Quadrajet and Holley SB. That combo, with hang-on AC got 17.5 or a shade more on the highway. I did NOT particularly have a light foot back then. If I felt like getting into it to enter a freeway, then I did. If I felt like passing some milketoaste, then I PASSED him.
 
it is not uncommon for a larger engine driven conservatively to get better fuel mileage than a smaller engine driven aggressively
 
340, 4.10 gear, A/T, .450 .455 cam.......9-10 mpg around town.

Don't know what it will do on the highway
 
This question has answers that vary widely and some I just can not beileve. Like the guys with 400 and 440 telling me they get 23 - 25 on the Hwy. Sorry, I just don't buy it, no way, no how.
 
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