I have a 09, Screw, 4x4, 4.6 3v with 115,000 miles and I noticed a 2-3mpg drop in my fuel economy in the city. I live in Gainesville Fl and drive the same route for the past year and a half (alot of stop-n-go traffic around 20mph), with the same driving habits. I track my fill ups on the fuelly website and it was there i noticed that my MPG dropped from about 11mpg to 8.5 now. I also run 87 gas every fill up.

My truck hasn't thrown any codes and the tires are all at 35psi. Nothing has been changed on the truck except for new plugs that where installed by the dealership.

thanks for any help yall can throw my way.

*note*
I did use the search bar but to no avail...

 

maybe your gas has ethanol added now

 

Never thought of that..

I tend to go to the same shell or PB stations and they both say (up to 10%E). Could have they gone from 4% to 8% with their mixes and that cause the MPG decrease? but still idk if thats enough E to make a 2.5mpg drop

 

I noticed a huge difference when my station started using ethanol, 3mpg drop wouldn't surprise me at all

 

Most gas has ethanol in it. It is mostly likey the blend change. During the summer months refineries add in a chemical that increases the burn efficiently of fuel (increase mpg and slightly lower emissions ) as mandated by the EPA. During the winter months ( when less people travel) they stop adding in the additive and mpg goes down. This also means gas prices should fall as well.

 

I have also noticed a decrease of 1.5 mpg in my 2012 ,5.0 and in my area and most all stations have 10% ethanol.

 

Here is a good article explaining the MANY things that hurt MPG in the colder months.
http://www.metrompg.com/posts/winter-mpg.htm

 

Mine went down 3 mpg from last tank, but my fun factor went up at least 20% zip

I filled up with E85.


Seriously though, you might check the plugs. The two against the firewall are known to foul out.