Gas MPG 83 250 I 6

[83C10OHIO]

Hi, I have a 1983 Chevy Scottsdale pickup with the 250 straight 6. I found an add on line that lists EPA est. MPG as 19 city and 25 hwy for an 81 with same engine. ( http://www.73-87.com/7387info/ads_GM/81_gmc.jpg ) .

However, I'm only getting 12 city and 18 hwy. I also have the TH-350 automatic trans, standard rear axle (256?) 1/2 ton long bed. Does anyone else have a similar setup and what kind of mileage are you getting?

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[Stewart G Griffin]

i've got a similar setup, the only thing different is i've got the crate 350 and dual exhaust.  But everything else is the same---2.56 rear and also if you've got a th350, it's a lockup version.

The other thing is, if you remember, EPA estimates before 1985 were kind of "jacked up."  The estimates 85 and on had to reflect "real-world" conditions.  Or something like that.

i remember going into a showroom pre-85 and seeing corvettes rated at getting 34 mpg.

18 is not a disaster, but it does concern me a little.

i will hopefully be able to report, accurately, what exact MPG i'm getting as soon as i install my digital speedo.  i went with a digital speedo because i need to know precisely how many miles travelled per tankfull.

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[Captkaos]

EPA estimates are calculated at 55mph on a level surface, with no A/C, and at an optimum temperature, not really hot, no really cold, No uphill or down hill at about 50/50 highway/city driving.  If you aren't driving at those speeds and you encounter hills and valleys, you use your AC, it is hotter or colder, well there is your difference. 

18mpg is pretty good though, keep in mind EPA modified their ratings so you can look up anything from 85-now to see what the real world estimates would be...

this is for my 87 R10 305/700R4:
http://www.fueleconomy.gov/feg/calculatorCompareSideBySidePopUp.jsp?column=1&id=3667

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[Fordeatinz71]

well, the closest i could find was for an '85 GMC K1500 with a 305 and a 700R4 and looks like i'm right on the money.  13 combined (i have gotten 13.6 out of it pretty steadily for a bit) and 12 city/15 highway...

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[the_legend_1981]

I have a 78 with a 250 and i say your number arent too far off.  All depends on how and where you drive it.

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[85MudMonster]

yep closest I could find to mine was a '85 K10 305 700R4 and it's combined was 13MPG which is my best MPG on the highway, in town I get about 11MPG and going through the Ozark mountains I got 9MPG....

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[Stewart G Griffin]

Preliminary findings for me, while not disasterous, are not too efficient either----15.46-15.47ish.

My setup:
350 crate (260 horse version)
set at 8 deg initial timing
stock top end---qjet, all emmissions and vacuum hoses ,stock air cleaner assm.
R45TS plugs
dual exhaust, stock exhaust manifolds.

TH-350C

2.56 gear

Off-brand tires

The engine is turning about 1800 at 55mph and 2100 at 65.  i rarely go above the speed limit and the secondaries stay closed tighter than a frog's

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[Dave Kay]

With your half-ton, 250-six cyl you won't get much better than what you're gettin' right now. In fact, you're probably getting better that most guys with ur setup. Like the other guys who posted said; EPA estimates are jacked WAY up--- forget 'em--- they're bogus!

I've owned an old '77 C20 for a LOOOONG time and with it's 4:11 rear axle and 292 L6 I never got better than 14 highway and mostly 9 or 10 city... that's unloaded and with a set of Clifford headers, stock Rochester carb. It is a stump-pulling truck fer sure but a gas-hog just the same as a V-8... if you're lookin' to get better MPG look into a fuel injection system for your six.. pricey, and prolly not cost effective... my $.02 cents!

Hope everybody's having Happy Memorial Day!

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[myet1967]

I have an 81 long bed with a stock 250 and th-350 lock up. Rear gear is 3.42. I put my tc on a 3 way switch so I can either put it in lock up full time in high gear, turn it off altogether, or run it on the factory vac switch. I drive 53 miles each way to work, on the turnpike at 75mph and average 16mpg out of it most of the time. Not that good when pulling my trailer though.

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