Gas millage dropping down from 18 MPG to 15 MPG

[Indyharleyguy]

Hi all my 1984 CUCV MPG has dropped for no apparent reason. I've replaced the air cleaner but not the fuel filter. I'm thinking
about taking a almost new fuel filter off a non working CUCV that maybe had 1000 miles on it before it was totaled and putting it on my running CUCV. I was wondering if that was a good idea or not?

 

[WWRD99]

My experience with an old fuel filter. My son bought a 1009 last year...dragged it out of the woods. Sat since 96. When I pulled the fuel filter off the mount it still had clean red diesel in it. That being said it depends on how long yours sat plus if it had bio diesel in it. That can mold up. If you're in a cold area try some kind of dejelling stuff. All of mine jelled up with the 5 degree days we had. All took some 911 then ran fine.

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[BKubu]

For the cost of a fuel filter, I'd just buy a new one so you are sure that the fuel filter is not part of the problem. My $.02.

 

[NDT]

You are looking in the wrong place. Fuel filter restriction = less fuel available = better fuel economy. Look for other issues like increased drag.

 

[Barrman]

Did you lock your front hubs in for driving in the snow? I agree about the filter not causing a mpg drop. There is more drag somewhere. Hubs locked, sticking front caliper, parking brake hanging on and similar.

 

[Jeepadict]

Winter blend fuel will decrease your MPG. Warm-up idling consumes fuel also.

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[biscuitwhistler37]

There's debate about failing glow plugs causing decreased fuel economy as well, I don't think it would be as substantial as 3mpg seeing as they're only supposed to kick on upon startup and something like 3 minutes into cold idle, but maybe. Check the wheel bearings as well, and "goofy" stuff like tire pressure, hopefully it's something simple.

 

[royalflush55]

Have you checked to see if the fuel tank or a line is leaking?

 

[dougco1]

For the cost of a fuel filter, I'd just buy a new one so you are sure that the fuel filter is not part of the problem. My $.02.

Have you "priced out" or tried "sourcing out" new oem filters for CUCVs? Advance Auto is asking $58.

 

[BKubu]

Have you "priced out" or tried "sourcing out" new oem filters for CUCVs? Advance Auto is asking $58.

A quick GOOGLE search turned up a Wix filter (WIX 33136) on ebay for $24.00 OBO plus $6.28 shipping.

 

[dougco1]

A quick GOOGLE search turned up a Wix filter (WIX 33136) on ebay for $24.00 OBO plus $6.28 shipping.

Is Wix considered an oem premium filter?

 

[BKubu]

Wix is a high quality filter. I have used them for years. I’d use them in almost any application.

 

[sbgarage]

Sticking caliper put me back in fuel efficiency, but a new filter change never hurts.

Wix and Baldwin are the cream IMO

We run almost any brand but shy away from Fram

 

[nyoffroad]

Some of the above is dead on, it's cold outside. What happens to oil and grease when it get cold? It gets thicker, from the oil in the pan putting more drag on the oil pump to the ATF in the tranny and TC all the way to the differentials and wheel bearings. The cold also effects the tires and sidewall flex and that also can effect MPG, while all the above changes as the truck warms up one thing doesn't change, cold air is denser. It takes more power to push that square box through the air than it does in the summer, speaking of power winter fuel has fewer BTU's due to being treated. Most all are small minor changes but when added up make a difference, ask any over the road trucker.

 

[Indyharleyguy]

Did you lock your front hubs in for driving in the snow? I agree about the filter not causing a mpg drop. There is more drag somewhere. Hubs locked, sticking front caliper, parking brake hanging on and similar.

Hi, no, this has been happening in two wheel high for a while now.
I will go ahead and buy a new filter just because I don't know when the old one was replaced, though

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[Indyharleyguy]

There's debate about failing glow plugs causing decreased fuel economy as well, I don't think it would be as substantial as 3mpg seeing as they're only supposed to kick on upon startup and something like 3 minutes into cold idle, but maybe. Check the wheel bearings as well, and "goofy" stuff like tire pressure, hopefully it's something simple.

Thanks the glow plugs were replaced a few months ago before I noticed the drop in MPG.


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[79Vette]

I've never got more than 16 mpg out of my 1009.

It was as bad as 11-12 when I bought it, and with brand new injectors, IP, front and rear brakes and wheel bearings all properly adjusted, all new steering, ball joints and alignment it's in the 14-16 range now. I also have an SM465/NP205 and advanced adapters Ranger overdrive, 3.73 gears and 33" tires, and a 6.5 turbo.

MPG went up about about 1 when I went to the manual trans and about 2 when I replaced the injectors and IP, but all the other mods did not have any affect on economy.

I hear stories of people getting 18+ in these trucks but I just don't see how it's possible. If you do figure out a solution I'd love to know!

 

[CARC686]

I would assume altitude reduces MPG, but I got an even 20 out of my 09 driving up and down the mountains. Flatland here is at about 4k feet. I'm running a HMMWV IP on a NA 6.2 with an open element air filter and turbo mufflers. I dump a quart of 2 stroke in with a full tank. Sounds like a lot, but a full tank is 108 quarts, so it's less than 1% and the IP likes it.

Edited to add it's overfueled with the HMMWV IP, which ought to hurt economy, but like I said, it reliably averages 20 MPG. Running open intake and exhaust made a big difference, no doubt. The intake is really loud. Sounds like a wide open throttle Quadrajet at all RPMs. The welded Thrush turbo mufflers are barely louder than stock.

 

[CARC686]

Just whatever you do, don't let a welder tell you it's a diesel, so you don't need mufflers. I mean unless you want people two miles away to think you have a big block.

 

[79Vette]

I would assume altitude reduces MPG, but I got an even 20 out of my 09 driving up and down the mountains. Flatland here is at about 4k feet. I'm running a HMMWV IP on a NA 6.2 with an open element air filter and turbo mufflers. I dump a quart of 2 stroke in with a full tank. Sounds like a lot, but a full tank is 108 quarts, so it's less than 1% and the IP likes it.

Edited to add it's overfueled with the HMMWV IP, which ought to hurt economy, but like I said, it reliably averages 20 MPG. Running open intake and exhaust made a big difference, no doubt. The intake is really loud. Sounds like a wide open throttle Quadrajet at all RPMs. The welded Thrush turbo mufflers are barely louder than stock.

I'm not sure about OP, but I'm at sea level and I have a turbo. Still gets 14-16 mpg.

And I don't have any mufflers and it's terrible. The downpipe comes off the turbo and dumps right behind the passenger front tire because I haven't had time to make an exhaust, and it's the loudest vehicle I've ever driven. Including my 396 small block Corvette with side pipes...