GREEN94

Hello! Recently acquired my Dad's F150 extended cab 4x4. He bought it new. Has the 5-liter with AOD, 114,000 miles. Dual tanks. Engine starts and runs fine, trans shifts fine though occasionally hard-shifts & drops out of OD... I've learned that's an issue with the speedo cluster that usually corrects itself but can usually be resolved by pressing the "Select" button on the trip odometer. It passed state inspection (New Jersey) about a month ago, so I assume the emissions are acceptable. But that's not why I'm posting this message. My problem is horrendous gas mileage. I filled the front tank the other day and topped it off this morning. Only drove 22 miles (local driving) but it took 3.5 gallons.... which means I'm getting a little over =6= MPG! My mechanic worked on it (new front brakes) a month ago, before I took it in for inspection, and since I had a Check Engine light, he found several codes:

P0171 - Something to do with an O2 sensor. I know one sensor was replaced several years ago, but still have one that's OE.

P0327 - Something to do with EGR

P0452 - VSS which I assume means vehicle speed sensor.

The Check Engine light comes on about 2-3 miles after I start it. I hadn't checked the fuel mileage prior to the inspection, and since it didn't fail inspection, I didn't troubleshoot it.

Though I'm accustomed to driving a small car that averaged 30+ mpg, I expected to see a big difference when I switched to this truck, but not to this degree. Fortunately my daily commute is only about 14 miles roundtrip...

While my Dad kept pretty good maintenance records, near as I can tell, he didn't track fuel mileage, and I can't ask him since he's now deceased... so I have no way of knowing what kind of mileage it should be getting. However, my brother has a '93 F350 Crewcab (diesel) that gets 11 MPG on the highway pulling a 32-foot RV, and nearly 20 MPG highway when empty. Though I don't have a diesel, to me this clearly says something is wrong with my truck.

Any and all suggestions would be appreciated. The truck has great sentimental value, runs and looks good, and I really would like to keep it for awhile.

LiftedTeal95

i would start by doing a tune up.

Brandon587

Yea, lack of a tune up, bad egr, and bad o2 sensors can cause very bad mpg, like you have. My 96 5.8 ext cab 4x4 gets 13 to 14 city and 16 to 18 (18 with no a/c and flat roads) on the highway. Your truck should be doing about the same. The vss problem could very well also be your problem with the truck coming out of o/d.

scottnbarbi

Plus, you may be doing better. These trucks seem to never take the same amount of fuel to fill the tank. at some stations they will click the pump off at just over 3/4 tank and refuse to take any more gas, and others top them right off with no trouble.
So, one or two tanks is not enough to know what kind of economy you are actually getting. From tank to tank mine can show anywhere from 6mpg to 20 mpg, but average of a few tanks works out to about 13.

GREEN94

I really appreciate the feedback. I haven't done a tune-up yet but know one was done less than 30K miles ago when Dad was still driving it. I checked tire-pressure (about 32 psi all around) and I think the air-filter is still fairly new. Looking through his maintenance records, I see the exhaust system was replaced (from the catalyst back) just 3 years after it was delivered. Is that typical for this generation? I take it that Ford didn't use stainless?

Anyway, I didn't have time to get to the O2 sensor, so I asked the technician to do it and check the A/C, which doesn't yet work. Before, the CEL would light like clockwork about 3 miles after starting the engine. Now, there's no light, and the engine seems to run differently, though it's hard to say how differently. Slightly smoother and maybe a little peppier? Nothing drastic.

I'll check the mileage this week and see if there's any difference.

GREEN94

I filled the front tank yesterday and did the math: mileage jumped from 6 to about 10.25 mpg (local driving) since the o2 sensor was changed. No codes were stored on the ECM. I still think it could do better than this... on the other hand I have to remember I'm carrying a A.R.E. TW-series cap that I'm guessing weighs at least 200 pounds, plus a bedliner, so... maybe 10 isn't so bad after all.

This is my first 4WD vehicle, and I read that this vehicle has auto-locking front hubs. Apparently, in 2WD, one would unlock the hubs by driving the truck in reverse in a straight line for at least 30 feet. That's fine, but is there any way of knowing that the hubs really -are- unlocked?

Thank you again to those who responded... any other suggestions on how to improve fuel economy welcomed.

GREEN94

The truck's now getting a bit over 12 MPG in mixed driving (90% local, 10% highway) after 3 tanks with Lucas fuel treatment. I'm thinking this is probably as good as it will get.

F-150kid

Have you tried sea foam? The stuff really works! It add 4mpg back to grandpas truck he has about 120k on his f-150! It added 3-4mpg back to my tuck as well and my f-150 has 198k!

Brandon587

Is local city,because for me local is county roads, highway, interstate, then city lol. Yea, 12 city is probably as good as its gonna get, but try seafoam, its good for the engine anyway.

nmanley80

I would suggest adding a K&N air filter and a manual hub conversion. With the air filter it is around $50 and you will gain 1-2 mpg and with the hub conversion from warn is about $200 and you might or might not gain any mileage but you will know that your hubs are free wheeling or locked just by a glance. I personly prefer manual hubs as they are less prone to breakage and are serviceable. Also with your tire pressure i dont think 32 is correct for your truck. look at the drivers door jamb and verify what psi you should be running and set it at that.