I just got my superduty Saturday. I filled it up completely. I drove 45.3 miles according to the trip odometer. and the gauge said close to 1/2 tank. Which didn't seem right to me so I filled it back up. Took something like $39.13 to fill back up but that was close to 10.1 gallons of gas. So my math brings me 4.5 MPG. I know I bought a v10, but it should be better than this! The truck has 148,000 on it. Has a k&n drop on filter. I noticed an slr performance chip under the hood and ripped that pos out! Tires are 285/70/17 help me please?!

 

4.5, shouldn't be there, unless you're romping on it and all you do is stop-and-go driving.

 

Sounds like something is dragging, check your brakes.

 

Could it be bad gas? i usually never run the gas i filled it up with because of a lot of pinging in my bronco

 

Your V10 will retard the timing if it pings, and you'll never hear it. Could very well be.

 

Ill fill it up with good gas next time then

 

Would changing the plugs help?

 

I'd check this over more than one fill-up. One time I got (hand calculated) 23 MPG with my '99 towing my trailer over a mountain (Washington) pass. The next few tanks showed that was an anomoly and there must have been a difference in when the gauge was showing "full". It never hurts to check your mileage often but I wouldn't go making changes based upon one fill-up mileage. Of course, if the problem continues this is not normal mileage for a V10.

 

Thanks everyone!!

 

Good luck...and keep posting back here as you solve the the problem.

 

I decided today to change the fuel filter. Seems like my idle isn't the greatest. I have to work later today so Sunday I'm gonna clean the throttle body and probably change the plugs and boots

 

Worst I have gotten is 6.8 mpgs over 1 tank and then 9.89, my average being ~8.35. This is just the first two tanks. so far. I have put 400 miles on my new V10. I just got this, it needs plugs I think because its got 170k on it and they have only been changed once. It does however, have new fuel injectors...i did notice this because they just looked brand new and bright orange.

 

The worst I have ever gotten was 7.6 mpg and that was towing a trailer with my foot in it, over a steep, twisty road for an entire tankful. It has gotten over 16 mpg once and can easily see 15 mpg freeway only. Typically it gets 11.9 with a 50/50 mix of town and highway. I often wonder what kind of driving guys do to see such low mpg's on a daily driver with no load.

 

stomping, going from 0-60....stopping...doing the same...over...and over....and over...

 

worst i have seen in the winter running 4x4 and lots of idle time is 6.5mpg.

avg in summer in 2wd is around 10mpg. city is 8-10 highway is 10-14.

i'd try running a few tanks and seeing what you get.