Toddrick

I've really given this 2003 v6 a lot of love, because it had been somewhat neglected when I got it with almost 100k miles on it. Replaced the PCV valve/hose, changed all necessary fluids, new IAC, etc. It runs great, the engine idles and accelerates smoothly, is plenty powerful and I'm pleased with my purchase for sure. But, I can't understand why I'm only getting 10mpg.

There are no codes in the system. I drive it gingerly to save gas, and put mostly highway miles on it (under 60mph usually) and it still uses almost 1/4 tank (25 gallon tank) to go 60 miles. It may be getting closer to 8mpg even, but I expected to get closer to 15mpg.

I picked the v6 in order to get better mpg--but it sounds like even the biggest v8's get better mpg than I do.

bobkyle2

You need to actualy check your MPG... You cannot go by what the gas gauge says.


Reset the tripometer and fill tank completly
Drive it until it reaches 1/2 tank or close
Fill the tank again, Take note of how many gallons of fuel you used.

Divide miles on tripometer by how many gallons of fuel it tookto fill tank this time.

Toddrick

Its an XL. I don't have any fancy stuff like a tripometer . The math shows about 8mpg, so 10mpg is a conservative guesstimate. I may be getting 12mpg best case scenario, but these are almost all highway miles, where I should be getting closer to 20mpg. Something is definitely off, and it can't just be my math.

I accelerate slowly from every stop, coast, and don't exceed the speed limit--this same driving style has me getting 5mpg more than advertised on my car. In other words, I'd probably be getting closer to 5mpg if I drove my truck aggressively.

I will write down the odometer readings between fill ups, and get more precise numbers, but I am certain I'm not getting good mpg. I'm not interested in discussing mods to get better mpg or anything like that, just curious what common problems might be causing lower than expected mpg.

bobkyle2

I have a 02 XL and it certainly has a trip gauge. My 08 XL has a trip also. They both have a button you have to press on the gauge cluster. I'm almost sure you have it if its an 03.


Either way, Do the math before you start diagnosing.

If its getting bad fuel economy it could have a bad o2 sensor.

Fordfan2006

Clean the MAF and throttle body too. That'll help along with the fuel filter and change the plugs and run some Lucas injector/fuel system
Cleaner in it.

Tackle

Those don't really help with mpg, but they're good maintenance tips.

03f15012

I've got the same motor in my 03, and it's progressively gotten worse. I was getting around 14.2-14.5. 15 with a little highway driving. Now, even WITH some highway driving, I've been getting around 13.2. So yeah, my mileage is terrible and has been getting worse.

RangoWA

My 4.6 was horrible, around 11 or 12 miles per at best. I replaced the TPS and adjusted it, fixed a small vacuum leak on a hose to the throttle body and cleaned the throttle body. I am currently near 18 miles per with mostly hwy miles.

Toddrick

Update: I found that I do have a tripometer at least, and so I filled it up, and reset it to 0. I was going to refill on the way home for a sampling, but forgot. So I don't have an official number yet. But I couldn't help noticing that the fuel tank was still reading full, after driving 60 miles. I can't confirm yet that the reading is accurate, but I am hopeful my mileage was greatly improved.

Check this out. I took apart the MAF to clean it this morning, but I found that I didn't have the correct Torx wrench, so I put it back together, and picked up the wrench on my way to work. So I get home, and begin cleaning the MAF, and noticed that I had left the air temperature sensor unplugged. Could this be why my mileage was (presumably double) improved? I plugged it back in, and cleared the error code, but I'm wondering if the problem is the IAT sensor...

Tackle

We can't assume anything since you haven't checked your MPG. Basically any info you've given us is pointless until you actually figure out your MPG.