Mileage Question
Thread Starter
Racer
Joined: Sep 2001
Posts: 352
Likes: 51
From: Austin TX
Mileage Question
I seem to remember reading somewhere on this forum that the average highway mileage for a c3 is ~20mpg. Even on the best of days, my 81 with TH350 gets less than 15. Am I misinformed, or is there something wrong with my car? Torque converter not locking up? At least gas prices aren't $1.80+ around here anymore!
Melting Slicks
Joined: Jan 2000
Posts: 2,386
Likes: 3
From: far, far away
Re: Mileage Question (Matt81)
My '81 gets 16-17 around town and 22-24 on freeway trips (when I behave myself :) ). I have checked the mileage of consecutive tanks of fuel running 70 mph with the A/C on and gotten an average of 24 mpg. This is with the stock 2.72 rear gears, 4-speed, and a Summit 330-hp crate engine. Mileage is a little better than it was with the stock L-81 engine, due mostly, I believe, to efficiencies gained from the higher compression (a little over 9:1), the more advanced timing curve, and the mid-range torque orientation of the Crane 2040 cam. But even with the stock engine, the car still got over 20 mpg on the freeway. And that's at higher altitudes (Utah, Idaho, Wyoming). Your '81 oughta do better than what you're seeing. I'd bet the carb needs a rebuild and your timing is probably not advanced as much as it should be.
Safety Car
Joined: May 2001
Posts: 3,758
Likes: 3
From: Surrey
Re: Mileage Question (Tom73)
I agree with Gator81 (Hi, Gator :seeya ). My '81 WAS getting just over 20mpg (imperial gallon) if driven sensibly. Dropped dramatically if I got a bit "enthusiastic" & wore my Lead boots ;) . After my locking torque converter keeled over the mileage has dropped to below 20. May be worth checking if yours is locking up OK. Does the engine need a tune up? Are you running under inflated tyres (that has a bigger effect on mileage than you'd expect)?
Paul
Paul
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Safety Car
Joined: May 2001
Posts: 3,758
Likes: 3
From: Surrey
Re: Mileage Question (Matt81)
Any tips on how I can check to see if my torque converter has gone the way of the dodo?
Good luck,
Paul
Drifting
Joined: Mar 2001
Posts: 1,411
Likes: 2
From: St. Louis, Missouri
Re: Mileage Question (UKPaul)
Also, you'll have to wait for the engine to warm up. The converter lock up function is temperature controlled and will not activate until the coolant has reached a pre-determined temperature.
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 278
From: Olmsted Falls, Ohio
Re: Mileage Question (Matt81)
I get about 15-16mpg with combined in-town and highway driving. Everybody "remembers" getting good gas mileage with the older cars, but it just wasn't the case in the mid-'70s. If you got 20mpg then you were not driving a 350 or larger V8.
