Improving gas mileage.
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Elder User
Joined: Apr 2004
Posts: 535
Likes: 0
From: Tucson, AZ
Improving gas mileage.
I have a '78 F100 300 I6, 3spd, 3:1 Rear. Mechanically it is completely stock. I am looking for ways to see real gains in gas mileage. I have done a complete tune-up, rebuilt the carb, new air filter, breather and pcv valve. Would headers with dual cats give me a noticable gain in gas mileage as in 2mpg+, any other suggestions?
Tuned
Joined: Oct 2004
Posts: 288
Likes: 7
From: Denver, Co
first question, what's your mileage now? and how do you run the truck?
Have to know what your starting with, - remember - yes it's a six cylinder, but it's a really BIG SIX cylinder.
I get about 14 around town with a 1970 flairside 4x4 with 4spd (and I'm thinking 3:70 gears, maybe 4:11's) - they will really limit what I can do mileage wise, - but the truck runs pretty fair.
Have to know what your starting with, - remember - yes it's a six cylinder, but it's a really BIG SIX cylinder.
I get about 14 around town with a 1970 flairside 4x4 with 4spd (and I'm thinking 3:70 gears, maybe 4:11's) - they will really limit what I can do mileage wise, - but the truck runs pretty fair.
Junior User
Joined: Dec 2003
Posts: 53
Likes: 0
Here's what I did to get better milage. I leave the truck at home when I don't need it and drive my '91 Festiva. I bought it for $100 and it gets 46mpg if I keep my foot out of it and go 55. Now that gas prices are up these little cars are more in demand, but I still see them for sale for around $5-700.
Cargo Master
Joined: Sep 2004
Posts: 2,691
Likes: 6
I live in CO and put in smaller jets in my 81. Increased gas mileage from 12 to 18 mpg. Here at high altitude (6200 ft) ther air is thin and the bigger jets were wasting gas since there was not enough air to burn the gas. Before jet change, wet black soot would spit out the tailpipe and the plugs were black. After jet change the exhause was clean and so were the plugs. Make sure you have clean exhause and plugs. If so then your jet size is right. A new jet was only $5.
