Well after a few tanks on the rebuilt whit trash its seems better. Will check it again this week and see if its better than the 11.mpg I got with the first tank. Do you think it should improve after break in.

 

I have a stock 2x4 2004 5.4 Lariat with 18 inch wheels, 20's going on soon. I just got back from a 300 mile round trip and did over 21 MPG on the way down. The results were via the MPG read out on the info center. I reset it only at fill up. Had the cruise control set to 72 with an occasional increase to 80. It seems that as long as I kept the RPM's below 2000 it did OK. Around town mileage is not as goog being around 15 MPG. Maybe on the trip down I had a tail wind, because on the way back I got a little less around 19.5, although there was more traffic and accidents which my explain it. The Truck has 45,000 miles on it, a slightly dirty air filter and I run 87 octane, if that helps.

 

The computer lies usually, check it by hand and report back.

 

Also - take into consideration if your tires are bigger/smaller than what came on it stock. If you have a GPS, you can check your speedometer's accuracy to the tenth.

 

I had my Garmin eTrex Vista with me and the MPH was just about 1 MPH higher in the truck then what the GPS showed.

 

Lots of information in this thread:

https://www.f150online.com/forums/sh...d.php?t=247794

Grim

 

So your mileage is actually a little over 1% lower because of the speedometer inaccuracy. I'd bet that the info center/computer is also being very generous with your MPG figures. All of em I've had weren't very accurate.

 

2006 Screw F-150 FX4 3.73's and 1200 miles. 13 city 16 hwy. All in all, it's hard to complain about that mileage in a 4 wheel drive 300 hp truck.

 

A few things come to mind here.

Remember when you fill up to make sure you are on level ground or the same pump, that can make more of a difference that any other thing.

I heard that running copper spark plugs will get you better mileage then the super duper platinum plugs, but they don't last as long.

Any of you running synthetics that might be helping?

 

2006 4.2L std tranny, i drive mainly highway, but short trips(5-20 miles usually)

i get 17-17.8MPG

 

Just took the trash to blythville Arkansas dove hunting and got 14.8 mpg running 65 to 75 mph. Last tank around town [ doing 90 a couple day while late for work] I got 11.8 mpg.

 

Just came back from Florida (3000 miles). Best I got was 17.3 MPG on 89 octane 10% ethanol blend doing 62 MPH.

98 Expy 5.4L all stock. It has 100,000 miles on it and still has the original plugs. I'm sure it will increase with new ones, but I ran out of time before we left. Now I can't get a comparison until we go on vacation next year. My wife's lucky if she puts 8,000 local miles a year on the truck.

 

That sounds about right. But there is elevation, load and other factors that play into the final result.

 

I've guesstimated about 18 highway and about 10 city with my '93. The 300 I-6 and a standard trans. Nothing to write home about, but it was a little better than I expected for a big ol' truck.

Synthetic oils also help, I swear. About 6k miled ago in my '96 Grand Cherokee I switched from regular to Castrol GTX full synthetic. Noticed almost a full MPG increase in average mileage from the last oil change, up from about 15.5 average to 16.4 over the past 6k miles. The oil still looks out-of-bottle tan too. For the increase MPG and the savings from getting 3-4 oil changes from one, I don't see why everyone doesn't use synthetics. Make sure you do it yourself, dealers always bend you over and forget the lube as soon as you mention you want synthetic oil put in. The local stealership said it would be $78.50 for a synthetic oil change. Drove over to autozone, happened to spy a deal for a free filter with 5 quarts purchase, and did it myself.

 

Elevation and load were constant. Half way through Virginia it was around sea level for the rest of the trip. Load remained the same except for a couple of souvenirs from Disney World on the way back .