Had the fuel filter changed 2 days ago. Noticed the fuel gauge was dropping faster than normal...checked the mileage...sure enough, went from 16 mpg to 11.9.

Is is possible the guy put the filter in backwards or something? It was replaced w/ an aftermarket filter.

At $3.72 / gal, I need an answer quick!

 

Check for a leak !!! A filter change won't change mileage.

 

I did...not leaking anywhere. I find it strange that the mileage dropped like it did within 24 hours of a filter change. If anything, I expected my mileage to go up a hair, not down by 25%!

 

do you smell fuel anywhere around the truck. the valve on the fuel rail may have gotten stuck when (or if) they relieved the pressure before changing the filter. i would just tap it down and let it come back up and make sure it seats good if it is leaking. (it looks like the valve on a tire)

 

Are you talking about the fuel rail that runs over the COP's? If so, which side...I believe there is one on both sides of the TB.

 

Maybe the guy drained a couple of gallons out for his lawnmower when he changed your filter...

Steve

 

I can only guess that you got your info from your overhead message display?
Before you had 16, and now 11. In such a short distance of travel that is most unlikely. More likely is that your battery was disconnected and the message centers "overall milage driven" has been erased along with the economy for those miles.
Now it shows only 11 probably because you drove only a short distance in the past day, and if driving off high way your economy is at 11. Check the display to see how many miles have been driven total in the computer. It might also be in the odometer trip counter .

Lowflyingbird

 

I have the old fashion odometer (no overhead message display). I calculate my own mileage. Immediately after getting the filter changed, I topped off the tank, and checked the mileage 2 days later. I drive my truck all day, everyday, and my mileage for the 4 years I've had the truck has never dropped below 15 (city or highway). I take that back, it did drop to around 14 mpg, but I changed the plugs, and it jumped back up to around 16.

I reset the pressure release valve on the fuel rail this morning. We'll see if that fixed anything...

 

Did you happen to fill your tank at a different place? Gas quality, Ethanol quantity? Up here in NY the quality of fuel is **** POOR!! The ethanol factor kills economy making you basically by more gas to burn, for all you greenies out there. Any good scientist / chemist will tell you that a lighter fuel produces less power. Cultivating it burns more power (diesel) that the ethenol could ever replace. If no other factor comes to light ,I can only sugest that you change the filter again ,either at the dealer, or just buy it from Ford and replace yourself. Maybe for some unknown reason it is simply the filter.

By the way, you mentioned plugs. You are NOT using Bosch platnums by any chance are you? If so change them out immediately. I have seen more bad Bosch single platnum plugs than anything. They have an exteremely thin electrode in the ceramic, and it basically burns up. It's very hard to see, but by checking with a fine enough wire, I first found a bad one. Since then I found many!!!

 

Is it possible some one stole gas from your tank? People suck you know...............

 

My 98 did the same thing when I changed the filter last... A few tanks later, it was back to normal mileage. I get 15-17 mpg, pending on my foot, and, for that little bit after the filter change I dropped to 11.

Can't explain it, I can only relate. LMAO!

 

it could be the higher fuel pressure affects the stuff the computer sees the parameters it runs every thing on. might be temporary.

 

Well, just as I thought.

I took my truck back to the place that replaced the filter. They claimed everything to be okay. Being the hard-headed guy that I am, their answer obviously did not satisfy me. I took their filter off (off brand- "Mighty". Stay away from this brand) and replaced it with the MotorCraft filter. MPG is back up to 14.8 as of this morning. Still not where it was, however, I did take it out of town this weekend through the hills of South Texas. I am sure over the next week or two, it will jump back up to around 16 mpg where it was.

I kept the off-brand filter, and will be taking it back to the mechanic that put it on, and hopefully get my $50 back...we'll see.

Thanks for everyone's input!

 

the added ethanol they put in fuel will kill ur gas mileage ethanol is makes 30% less power than regular petrol gasoline when u add 10% to the mixture your basically loosing 10% fuel efficiency i noticed that i my car alone that in the past 8 months ive lost 4mpg. because of the stuff they put in it now to thin it down.