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How to improve 5.8L Gas milage?


Old 01-14-2004, 05:12 PM
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Join Date: Jan 2004
Location: MN
Posts: 6
How to improve 5.8L Gas milage?

Okey I have a 1990 F150 5.8Liter 351 CInch truck.

My truck is my winter beater and Im looking at trying to get better gas milage out of it. I think it has a 18 or 19 gallon gas tank (short bed) (not extended Cab). And I get about 190 miles out of 18 gallons (with about 1 gallon reserve)

So 190 miles to 18 gallons.. with no load?

Anyways I replaced the airfilter about a month ago but am not really sure what else I can do to help safe a little bit. I dont drive it hard, it has 130,000 miles on it so I take it really easy on it.

I did a search on this forum but I couldnt get "better gas milage" to come up because of minimum letter usage or something.

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Old 01-15-2004, 02:52 PM
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Join Date: Nov 2001
Location: Fort Worth
Posts: 200
Try searching with just better mileage. You will have to sift a bit. Here are a cuple of the latest posts.

Better Mileage

Better Mileage
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Old 01-16-2004, 07:34 PM
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Join Date: Jul 2002
Posts: 462
Thats about right.

Yep, that sounds about right.

I've got one of those. Put a reman in it, new plugs, new wires, air filter etc. She gets 10.

You have to look at the bright side, it doesn't matter if you have a trailer or not, you still get about 10.

Honestly, you just wont get much better fuel econ out of it.
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Old 01-16-2004, 08:57 PM
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Join Date: Jan 2003
Location: In the South
Posts: 202

My 351 (1993 F150 4x4 E4OD) supercab gets roughly 12 mpg
or maybe 13 if I lie a little. 141k miles on it and it has never changed much at all.
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Old 01-17-2004, 02:50 AM
Join Date: Dec 2003
Posts: 29
I have 7.5 (460) I get 11 mpg in highway only. In city, I get 7-8.

I would expect 5.8L to be better, but not much. I would not be satisfied with anything less than 13. Especially with OD tranny --- I have 3-speed C6, which is even worse.

Looking at the ford material from '90, 5.8L is has almost as much HP /torque as 7.5L. Well , not really, but it is fairly impressive for a small-block V8 vs. big block.

7.5L and 5.8L are both very very thirsty engines.
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Old 01-17-2004, 02:54 AM
Join Date: Dec 2003
Posts: 29
You need a tuneup:

Air Filter,
Fuel Filter,
Oil Change/Filter,
New PCV,
Spark Plugs/Wires,
New Cap/Rotor
Change oxygen sensors with OEM
Check EGR valve
Remove and clean Throttle Body/MAF/IAC,
Check condition of Brake Pads/Rotors/Hardware,
Flush/Bleed out all old Brake Fluid & replace w/quality fluid,
Flush Cooling System & Fresh Anti-Freeze
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Old 01-21-2004, 02:58 PM
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Join Date: Jul 2002
Posts: 462
Just for perspective, I thought I'd get better economy from my '03 5.4L with 10,000 miles. If you call 13 better, then yes I get better.

Don't waste too much money trying to save any.
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Old 01-22-2004, 08:54 AM
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Join Date: Jan 2003
Posts: 150
There is a way to get a couple of miles per gallon out of the 351s, you can have a mass air system installed on it, converting it from bank fire injection to sequential injection...
It would only cost about 1200.00 or so,, and only take about 70 thousand miles to recoup your investment.. Ok,, bad idea..

My 351 Lightning gets 14 on the highway if I take it easy,, 10 in mixed driving and about 8 if I am pulling a trailer.
They like fuel !!
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