o4 lariat 4x4 screw 5.4, 3.73 ls. i was getting about 15 mpg in town with 8,000 miles on my truck and then they changed the pinion gears and clutch packs and my milage has stadily dropped to about 10.5 mpg in town. they did the reflash and it did not help. they told me that it is the winter blend gas that is causing my milage loss. i think it has something to do with the rearend that is messing it up. i also have found foam in my oil cap and they said that is normal because of the moisture from the cold weather, but they would keep an eye on it. it still runs real good but the milage just keeps getting worse. 13,500 miles on it now wish it had the same milage when new or better it was 15 mpg in town and 21 mpg on hywy, now it is 10.5 in town and 17 on hywy. the digital read out use to say 520 miles to empty when full and now it says 380 to empty when i fill it up. (and the dealer says oh you can't go by that)its pretty close when i figure it out. otherwise why would they put it on the truck.(just to make it look good) i don't think so.
Last edited by polaris4x4ex; 12-15-2004 at 12:25 AM.
Polaris...believe it or not, there is a break-in period for the diff. There was a post some time back where a guy used a thermal sensor and his first couple thousand miles the temp was almost 200, after that it was down to lower 100's. That heat is the result of friction, and your engine is trying to provide the power to overcome that friction. As a result, more energy is required, so you burn more gas.
Using the computer to figure your mileage is not going to give you an accurate assessment...the only way to accurately gauge your MPG is to record the mileage, fill up, go through a tank, record the mileage again, and fill up. I do that every time I gas up, dividing the miles driven by the gallons added, and come up with the same range of (rather depressing) MPG's. The on-board computer display is for ball park guesstimates...too many variables can affect the computer display at any given time.
The oil foam in the filler cap caused by moisture?? That's not a good thing in my eyes...oil and water are never a good thing!
i do figure out my own milage and have been keeping records the last two times to prove to them that it is that bad. they said they hooked there computer to it and drove it around town and it said i was getting 15 mpg. as for the foam in the oil fill cap, i've never had that in any of my other vehicles. they said it was from the oil fill tube being plastic to the metal valve cover was why the moiture was there and it would not hurt it. i had them document it on my paper work because i think that might be why my milage is so bad. they said they have looked at several other motors that people have brought in and the foam is in there's to. its normal. (i don't think so!)
Don that was me checking the rear temps with an infrared heat gun. Yes it was hot when it was new, but I don't think thats his problem..
If the rear was dragging the mpg down you'd feel it. Take the truck out of gear just before you stop and let drift to a complete stop by itself. If it stops without gradually slowing down to nothing then something's binding, but for it to pull the mpg down 5mpg it would have to be dragging pretty good.
Boy, I love gas mileage posts. Those that know of me expect to see me post here. 11.6 after reflash. My truck is within "spec" so I am told. My best 14 mpg all hiway. Bitter?....yes. Thanks for letting me steam.
Dunk...thanks for the info (sorry I didn't credit you directly, I forgot who posted it originally).
I thought that would be the most likely cause of decreased MPG, since his was decent before getting that work done.
Triton-IC...I've been following your MPG problem since you first mentioned it. I've even asked the vehicle techs at work. Nobody can come up with a reason. It's definitely not where it should be called "within spec". Wish I could help there!
When I got mine reflashed, I went from ~12.5 mixed to ~13.5...not a great improvement (that could just be the eng breaking in, also). But this is one heavy vehicle (my config), so I dont expect to get much more.
Have to disagree on the computer statement, after all it's doing the same thing. In fact your the manual method could be less accurate why, because I doubt it gets filled to the same level all the time. Fill up on a cold day vs a hot day varies the density. The computer measures actual consumption vs the mileage. If you reset at every fillup it will present very accurate information.
One other point ,I have checked on numerous occassions to see if the computer is correct, it comes extremely close to the manual method!
Boaters rely on their fuel consumption meter all the time, because the fuel level gauges are not accurate, nor is the manual fill method!
Polaris - moisture can be from condensation buildup internally depending on where you live. Check the PCV also.
I have always been critical of the computer readouts, and they have not always been right. On two Caddys and two Grand Cherokees 90% of the time they claimed 1-2 mpg better than the cars got. But on this truck it's dang close.
Your also right about not filling to the same point. Since my tank was recalled, filling it up is a joke. Sometimes you can add 3+ gallons after first shut off, other times half that. I have to average two or more fillups to see what I'm getting. Not to mention temp of gas causing expansion/contraction.
plus every nozzle is different.
Since I added a Scangauge (1500 miles ago) giving me access to the trucks computer the trip mileage has been on the money.
Boaters rely on their fuel consumption meter all the time, because the fuel level gauges are not accurate, nor is the manual fill method[/QUOTE]
Kevin you are right about the fuel consumption meter's on boats, but they give you specific gallons burned and gallons per hour being burned.. They are quite a bit different than the fuel computer in these trucks. These things try to average the fuel burn and figure mileage at the same time. The manual states 500 miles before it's dependable. As long as you understand "average" since you hit the reset button they work well. I think an actual gallons burned meter would be better.
Any of them are a guess until to have the pump nossel in your tank. Yeah, Weights and Measures Division in any state are suppose to be checking gas station's for their pump accuracy's,,,,but?? Your best shot at filling your tank is to be parked in the same position, pointed the same way at the same pump in the same gas station as you filled at before.
I think when we are talking fuel expansion from a 50 degree difference between winter and summer you might be talking a few ounces of capacity on 20 gals of fuel. I don't think it's much of a factor.. Most times fuel coming out of underground tanks is pretty cool anyway and if you are using the same gas station temp is not a factor..
Does anyone have any GOOD news about the MPG of the F150??? I'm starting to doubt whether or not I want one anymore! I wholly understand that it's a truck and it won't get volkswagen jetta mileage but I think 15-16 city is a reasonable request! I've heard that it takes a few thousand miles for these new tritons to "break in" enough to get good mileage. I've anywhere from 3000-60000. Any input on that?
I'll let you figure it out, 04 SCrew, 4.6, standard truck. 506.4 miles filled to the top with 22.6 gallons of Shell unleaded. Combination town and expressway driving some of which is at 85+ mph. Just don't ask me how I like the howling rear end and a huge list of other things that is making look for a different truck. Gas mileage? That's the best thing about my Ford, okay, it's the only thing I like about it.