Why am I only getting 12.5- 14.5 mpg? I use premium gas, Royal Purple motor oil, 35 inch tires, flowmaster exhaust, replaced the Y pipe for better flow, drop in K&N fair filter. I know my new tires are heavier than OEM, but still. I'm seeing others with bigger tires getting better mileage. Something must be wrong? any suggestions?

 

All city driving , stop and go traffic.... are you in to summer time gas where you are??

 

Number one killer of fuel economy is driving habits.

But, the 35s are a big reason and I suspect that most guys claiming stock-like MPGs who are lifted and running 35s are basically either mathematically challenged or have veracity issues.
I lost a solid 4 MPGs when I lifted my truck and went to 35s. Gained 1-2 back when I changed my gears (even though MPGs wasn't the reason I did it).

Also, what flow you gained by losing the restrictive "Y" pipe, you gave right back by installing a muffler with a really poor CFM rate.

Winter blend gas is also a killer, as are under-inflated tires.

Also, if your speed has not been recalibrated for tire size, you are not getting a true MPG reading...

 

I did not know there was summer gas and or winter gas...?

 

I guess I have a lot to learn, I bought my flowmaster because I new it would sound good. where can I find a chart that show CFM of various mufflers

 

I have 2000 miles on my truck and I'm getting 16.2 MPG on the highway. I don't even bother to check in city driving. I'm a pretty conservative driver when it comes to take-offs and highway speeds. If I pickup another 1 MPG or 1 1/2 MPG when it's broken in I'll be happy.

 

More than likely it has to do with your driving habits and the roads you drive on. If you live in a hilly area, you're not going to get as good of MPG. To me these questions are just ridiculous. There's too many variables taht affect MPG. I seen the post where the guy said he was getting better MPG and he lives in Canada, so he doesn't even live in the same area as you. There could be a number of reasons why he's getting better MPG than you. As for the "summer gas" vs "winter gas", see the link included.

http://auto.howstuffworks.com/fuel-e...mmer-fuel1.htm

 

https://dodgeforum.com/forum/3rd-gen...mparisons.html

 

Because you bought a big gas guzzling truck and put big tires on it. It's to be expected with a truck like that. It'll be better in the summer time depending if you use you A/C alot or not. I don't pay for my gas half the time so i dont really pay attention to my mileage.

 

I seen the post where the guy said he was getting better MPG and he lives in Canada, so he doesn't even live in the same area as you.

He may have been referring to the fact that our gallon is 20% bigger than your gallon, so our numbers are always higher.