2001 5.4 SCREW

Here's what's new.

Iridium plugs
New coils
High flow CAI
High flow summit exhaust
Mobil 1 oil changes regularly
Clean MAF w actual MAF cleaner
Street tires
Drives perfect...

.... But still only getting 13 mpg with mostly highway, not in 4wd.

What gives???

Frustrated!

JD

 

how many miles on it?
O2 sensors working ok?
Injectors ever been flushed?

 

Where do you live and what type/lengths of trips are you taking?

 

Even if a O2 sensor doesn't go bad, it still needs to replaced every once in a while. They aren't like super cheap. I would look into replacing them. Also look into having a transmission filter and fluid change, and maybe go ahead and have your rear diff serviced.
I know our trucks like platinum over iridium.

 

Also! Fuel Filter!

 

That's what I get in my 02 regularly. I have a friend that gets the same in his 04 FX4 and it's not even Supercrew with less then 80k miles. That mileage seems to be the average. She is thirsty!!!!!!

 

Fuel filter, new transmission fluid, and O2 senors. Winter fuel will always bring mileage down a bit also.

 

Me too. High 12's-low 13's. But I also don't drive with a "soft" foot,to be fair about it.

 

Actually summer fuel brings down mileage. Summer gas has a ethanol blend as much as 10%, where as winter gas can't have more than 1%, none is some areas.

 

You obviously haven't lived where it gets cold during the winter. There is a 5% blend of ethanol in the summer here and the winter fuel still will bring mpgs down every year.