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Old 04-07-2007, 10:44 PM   #1
C10 - C90 Bill
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'71 K-20 Gas Mileage

I'm looking at a '71 K-20 4 X 4 with a 350, 4-Barrel Q-J, and a granny gear 4-Speed trans. Not sure of the rear gears, but they should be typical stock.

What would you all say the typical gas mileage would be on a truck like this?
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Old 04-07-2007, 10:57 PM   #2
dave2953
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Re: '71 K-20 Gas Mileage

I would guess 8-10 mpg. I guess it depends on how well it's tuned and how heavy the driver's foot is.
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Old 04-07-2007, 11:10 PM   #3
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Re: '71 K-20 Gas Mileage

Yep, 8-10 if all's good. Tired, out of tune or low on power you can expect much less. My '72 with the 500 Cad doesn't really use any more gas than it did with the original 350. The best I ever got out of one was with a SB 400- it would get 11-12.
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Old 04-08-2007, 12:13 AM   #4
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Re: '71 K-20 Gas Mileage

Appreciate the info y'all.
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Old 04-08-2007, 12:22 AM   #5
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Re: '71 K-20 Gas Mileage

i'll brag a little. my EFI'd 496 got 13.2 on my last road trip. around town I get 8-10 though. but I culdn't be happier, except if it cost less.
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Old 04-08-2007, 12:31 AM   #6
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Re: '71 K-20 Gas Mileage

10 - 12 seems to be the average on these trucks... but, the average truck isn't a 4X4 either.
I'd say 8 - 10.
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Old 04-08-2007, 01:28 AM   #7
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Re: '71 K-20 Gas Mileage

I agree its about 8-10 mpg on my K20 as well. I put on a heavier throttle return spring and changed my driving habits and it has gotten better. I try to have it into 4th gear by 20mph.

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Old 04-08-2007, 04:14 AM   #8
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Re: '71 K-20 Gas Mileage

i get about 8 city and 11 highway (2wd)
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Old 04-08-2007, 10:45 AM   #9
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Re: '71 K-20 Gas Mileage

I figure around 10mpg,don`t really want to know.It`s way better on two-lane hiways where I`m good at 50-55 mph.I get on the interstate and roll 65-70 and listen to it guzzle.I like to just "bop" around in my 4spd truck and enjoy it`s un-modern old-real truck feel.Driving country roads at 40-45 mph I`d say I could get 12 mph.I have 4.10s and 35" tires,that`s my o/d.
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