To start this post off. I have used the search feature.

I have a 2002 King Ranch Supercab 2WD 4.6l with 122k.

I have had this truck since 72,000. When I first got it I was getting 15-16 combined(70-80% highway).

Since then I have replaced the muffler with a flowmaster and put in a KN filter and removed the silencer.

I have recently replaced plugs(no wires. It is direct). Fuel filter. Oil. Pcv valve. An all around tune up. Even done fuel system clean at Firestone.

I have run 5 tanks through with approx 85 degree weather. 75% highway. All flat. No humidity. And normal driving. Which comes out to anywhere from 13.5-15.3.

Then I replaced my 70 MPH highway driving down to ONLY 55 MPh. And I got 11.2-11.4 on two tanks.

This baffled me. Does anyone have this same problem? I should be getting closer to 15 normally. My 94 f150 got better than this.

Thanks.

 

Mine is a 03 reg cab short bed 5.4 with 45k and has 13.7 from 2 tanks so far...

 

Its the Gas that your putting into it. The Fuel with 10% ethanol decreases the real world fuel mileage as much a 27%. Of course the oil companies won't tell you this. Do yourself a favor and go to a gas station in your area and fill up with gas without ethanol and then see for yourself. I bet you will be back in the high teens.

 

Is it also possible that the 55 mph speed puts you at the margin of the OD and the transmission is downshifting out of OD on hills and such, due to the lack of torque at the lower engine speed?

 

Totally agree on the ethanol thing. I did my own test when i was able to get ethanol free gasoline.... I had not seen ethanol freegasoline now in a long time

 

There is a website and an app called pure gas, it will show you the gas stations in your area that have ethanol free fuel. They sell ethanol as better for the environment and about ten cents a gallon cheaper, which in a 25 gallon tank will save you $2.50 up front. My real world MPG tests have demonstrated time and time again that in my 5.4 liter I get 13.5 MPG vs 10.7 on ethanol. That's almost 30% better fuel mileage on pure gas. So the initial savings are a joke compared to the real world savings.

Meaning 10.7 x 25 = 267.5 MPT vs 13.5 x 25 = 337.5 that's a difference of 79 miles a tank at 13.5 miles that's 5.18 gallons saved at 4 dollars a gallon that's $20.72 in my pocket everytime I fill up.

You guys don't believe me, just go out and due your own test and see that crap that the oil companies are pulling on the american public.

 

Also if you can put 87 octane, that helps it run a little cleaner.

 

I've never heard of the ethanol thing. I'll look at that website and try out some ethanol free

 

The problem in many areas is that there are no stations that sell ethanol free gasoline. I downloaded the app and the nearest station is 153 miles from my home.

1 gallon of pure ethanol yields 2/3 the energy of 1 gallon of gasoline. Vehicles that run on E85 typically experience a 30% drop in their MPG when compared to gasoline. E10 is not as bad, but still has lower energy than ethanol free gasoline.

See web site below

http://zfacts.com/p/63.html