I have a 2001 Supercrew 5.4L V8. I purchased it new in 2001. It has 91K miles.

I have only had 1 issue with this truck. About 2 years ago a coil or something that the spark plug fits into went bad and had to be replaced. During that time, before taking it in, I changed he fuel filter. They did a full fuel system flush and replaced all the spark plugs.

Other than that, I have basically added new tires, changed the oil(about every 5K) and drove it.

Back in the summer I put new Michelin tires on it and replaced the air filter with a K&N filter. Right after I did that my gas mileage increased significantly. Usually my low fuel light comes on at 315 miles but increased to 335 for a couple of tanks.

Soon after...maybe about October or so I noticed my mileage dropping. That was about the time it starts getting cooler here in KY but not cold. No changes were made in my driving conditions, I get gas anywhere(cheapest price I can find) and always have. Now however, my low fuel light comes on at 280.

I thought it was something funny with the sending unit from the tank cause you could see the gas gauge fluctuating. I pressed on and ran out of gas at 327 miles one day. So it is legitimately drinking fuel.

I am at at loss. I got no idea what it could be. I have called the local ford garage and they didn't have much input.

I don't know a ton about engines. I am grasping for straws here. Could the new air filter cause it. I read somewhere that someone though the oil from the air filter(they are covered with a slick substance) could have covered an oxygen sensor....apparently they thought it had happened to them. If you get less mileage in the winter, is it because of cool weather and does that filter allow too much cold air? Should I go back to a stock paper filter?

Also, I have some fluid leading from the middle of my real axle. Looks like oil actually. It is not pink. Could that be a seal bad?

I would appreciate any insight that someone may have.

Thanks.....paidfor

 

Try cleaning the MAF. Bad thing about the K&N filter is the oil from it contaminates the MAF sensor. Take it apart carfully clean it and reboot the truck. E85 might be a factor to. If you ever clean the K&N be aware that freashly oiled and over oiled ones get the maf dirty..

 

The winter blend drops mileage considerably. 1-3 mpgs' I have lost 2 or so.

 

sorry I am stupid...what is the MAF? Would I be better off to change back to stock or if it is contaminated, would it just make it worse?

 

I just think it seems odd....it has never happened in 10 years. Is the the first time winter blend has been used.

 

Mass air flow sensor. its located right next to the air filter just down stream. Un plug it from the harness and remove it from the air filter housing youll need a safety torx I think it might be a t20 to get it apart. Spray it down with maf cleaner do not touch the wire youll ruin it. Theres a how to around here but i cant find it.

 

It's the winter blend fuel. I'm betting yours is 10% ethanol.

 

Is this the first time we have had a winter blend with 10% ethanol?

 

Not a clue - ask them at your local gas station.

 

you get 14+ mpg?? i get lucky to get 12!
I have a 4wd.. is yours 2wd or 4wd?

But i think i need to have everything of mine cleaned.

 

2wd

I could legitimately get around 330 miles on a tank of gas typically.

 

o thats why. 4wd guzzle more gas.

 

I just drove 300 miles on the highway at about 75 mph. Got about 13.6 mpg this trip where I usually get 15 mpg. I was getting 16-17 a year ago, but with 160k miles, maybe it's getting tired. I'm sure an induction cleaning is needed, but hate spending $210 for one.

 

run some gas cleaner thru on your next fillup. it will help out

 

I have a 99 f150 4.2 with 168K on the dial. The other day the "Service Engine Light" came on. The code I got was a P0174 bank 2 error code. I have cleaned the MAF and am replacing the plugs and wires. I am also going to test and replace the o2 sensor i think is bad. But when I look at replacements, I get 3 different heated ones? Without pulling, is there a factory number to help me with ordering a replacement before pulling? Or does it matter concerning 02 sensors?