I have a 99 SD 2X4 regular cab with a 5speed tranny. I get around 13-15mpg on the highway. What's worng with it ?

No check engine lights and it's all stock.

The only thing that it does is thats ometimes, I I accelerate real fast it sputters a lilttle, sounds like it skips timing.

I put new plugs and a new fuel filter - Still the same

Other than that it runs great !

 

Have the computer scanned for codes. I personally, would go to a dealership for that. Could be an injector, mabey an professional injection cleaning would help.

 

Did you have tuhe truck checked at a dealer or a regular shop. ?

 

Clean the MAF - that might help the sputtering... but might make the MPG worse

As to the 13-15 MPG, my V10 gets that, and I've heard that the V8 doesn't get much (if any) better MPG than the V10. Sounds about right for an SD, by the way...

What gear ratio do you have in the rear?

art k.

 

13 mpg sounds low, but 15 is not out of the range of normal depending upon how you drive. For example, if you continuously speed up and slow down on the highway, you can seriously degrade your gas mileage. I suggest that you do careful calculation of your mileage while paying close attention to your driving technique. Use the speed control if you have it. If you find that you are getting 13 mpg on the highway with reasonable driving habits, you may have a problem.

I just took a 2,200 mile cross-country trip in my '01 Expedition with the 5.4L, and it averaged 16.3 mpg (by hand calculation, not overhead computer). We drove at a speed-controller-held 75-85 mph on the interstate, and we took several side trips to see the sights.

According to the overhead mileage computer, this Expedition averages about 14 mpg in daily driving with a mix of in town and highway driving. Since the Expedition has an automatic transmission and is probably at least as heavy as your truck, I conclude that 13 mpg highway mileage is on the low side for your truck. Something in the drivetrain might be causing excessive friction, or the ECM might not be managing the engine correctly. The sputtering on acceleration suggests a problem with fuel/air management. Get the codes, MAF, and injectors checked. You might also check your exhaust pipe for a black sooty residue which could mean the engine is running rich. If you suspect the engine is running rich, but no code confirms this, the ECM may be malfunctioning. Your dealer should be able to analyze these things . . . but I wouldn't accept that 13 mpg on the highway is normal . . . 15 mpg is another thing, depending upon how you drive.

 

Well Bud,
I have a 5.4L Supercab auto. I've driven it for 2 weeks straight keeping the tach under 1500 rpm. I've driven it for 2 weeks straight stomping it and running up to 5k on the tach. I've driven it 100 miles at 80 mph on cruise control in flat Florida. In all three of these scenerios, the mpg was 12.

The local Ford dealer had the truck for a week so the Ford Fuel Engineer could come and diagnose it. Diagnoses: "There's nothing wrong with it. Its getting 17.2 mpg (according to his computer on an 8 mile road test), which is within the expected range. There are no adjustments that can be made to the engine. That's the best it's going to get."

One of my co-workers recommended a super chip and a cat back exhaust system because that helped his Expedition. The question is am I going to keep the truck long enough to benefit from the investment?

 

How's your air filter?

What tire pressure you running?

When did you notice a change (if any) to your mileage?

What kind of load do you carry?

What kind of terrain do you drive in/on?

How many miles are on the truck?

What weight oil are you using?

When did you last change it?

 

I have a 2002sc 4x4 5.4 and just gor 550km's on a tank.half highway and half rural roads....with a I think a eighty litre tank...that's about 18.5mpg....with 95,000km's on the odometer.It's also the 7700 version which has the 373 gear in the back instead of 3.55......goodluck.

 

I checked the mileage on a road trip to kansas...


the truck has 145k

It has always been like that but I only had it for 3 months...

what pisses me off is that my dad has a SD 4x4 v10 extcab and he gets better mileage than me.. so I know something is wrong

 

I have a 2000 F-250 SD 4x4 with the 5.4 engine,I get 12 miles to the gallon around town.I have the 4.10 rear axle.The rear axle ratio is critical to fuel milage.

 

Perhaps the speedo is reading slow which will give you inacurate readings. My 01 F150 SuperCab 4x4 5.4L 3.55 gears got 15mpg on my last real road trip. It seems to be better now with my Diablosport Predator. I hauled about 6500 lbs of cut wood 160 miles and got 15.4mpg. Go figure, it is about the same loaded with OD locked out as it is empty in od.

 

Yeah. What he said. Accurate speedo is essential to obtaining accurate mileage calculations. If the tires on the truck have been changed to a larger diameter, your odometer will be registering fewer miles than you are actually traveling and your mpg calculations will be lower.

 

I have a '00 F250 SD 4x4 Super Cab, 5.4. I average between 8-10 mpg, consisting of mostly short trips and hauling 8-900 lbs of hay about a mile one way every other day. It's an automatic, with 3.73 gears and a K&N air filter. I believe I have reasonable driving habits (as reasonable as they can get for me being 17 ). I might be getting an after-cat exhaust and a full intake soon. Any suggestions that might help my mileage out?

 

To average, say, 13-14 mpg in mixed driving, the 5.4L gets up to about 17-18 mpg under liesurely highway driving conditions, and it gets probably about 10 mpg on local stop-and-go trips. However, it does worse than 10 mpg when not fully warmed up. So, if all your driving is short trips that do not permit the motor to warm fully, maybe 8-10 mpg is normal. In addition to the other suggestions made in this thread, you could try to organize your trips so that the motor does not cool down between them.

 

Thanks for the info scot. I'll try organizing my trips a little better from now on.