might try posting this question in the V6 form and start a new thread. Sounds like you might have a vacuum leak, check the PVC hoses for leaks..

 

Your O2 sensor is fine. It's doing its job REPORTING a lean condition.

 

I just had my 2010 F150 oil changed at my local Ford dealership. I lost over 70 miles per tank after they did the work. I only have 200 miles left on my warranty and I'm worried this may continue. Has anyone else had a similar problem? I was getting between 500 and 520 but my sensor now shows about 450 after filling up. The mileage also has changed at times during the same drive. What's up with that?

 

Why did you post this in a thread in the 1997-2003 forum?

 

I am guessing the MAF. I too have the K&N in my '98, 4.6, 2x4, reg cab. It is easy to put too much oil on these after cleaning. I always let it dry overnight before I put it back on. btw, I averaged 17 mpg on my last trip from Mpls to Dallas.

 

Everyone is over looking the issue. Fuel no longer has 10% ethanol anymore, it now required that all states use 15% ethanol added. Your mileage drop is due toe many things. But not a air filter.. Age of the vehicle is number one. and second is fuels being produced now days. Around this time last my 4wd F150 was getting close to 21-22 mpg on the interstate, now i'm around 15. Its all because of fuel..

 

I think you might be right. Check out this article from Consumer Reports. The Flex Fuel vehicle dropped from 21 to 15 MPG with Ethanol.

http://www.consumerreports.org/cro/c...view/index.htm

 

Not yet. It is now ALLOWED, that's all.

 

The poster brought back an old thread from last winter.
How does it apply in summer weather?
Start over again for the present conditions.
Ethonal releases more oxygen upon combustion.
The OX sensors detect this as a leaner condition and report it back to the PCM where the program acts to 'increase' the amount of fuel injected hence the loss of fuel mileage.
Alky in the gas was never a wise thing for the gov to mandate.
It was a misnomer to begin with and politics got into it to the point now it won't be retracted.
Bottom line is they thought it would help clean the air but when the motor uses more fuel, that is very questionable for the end result of cleaner air.
The other result of this is your burning you bread and other food stuffs and caused food prices to rise from competition between fuel and food.
The farms that raise the corn have a market either way so it's not about jobs.
When the gov dictates, you lose.