My gas mileage is gone, what happened?

[neverhme]

What happened?, as you can see it was good for a HD,since then I put a drop in K@n filter and had new tires installed, tires were oem size goodyear wrangler kevlar A/T. I cannot seem to get over 12.4 on the meter no matter how I drive, I reinstalled the stock air cleaner today but cant grip the k@n being a problem I have used the k@n in other engines without issue, truck is a 2015 2500 6.4 hemi, I ONLY have 29k miles on it but frustrated, am I missing something, No codes no issues, tires all set at 65psi. I guess I should mention it has the mbrp duals .

 

[JoshsRam]

I'm gonna go with Space Aliens. Yeah, that's the ticket. If you want a serious answer though, you need to provide more details, it is anyone's guess without knowing the details of ANYTHING about the picture you posted. Did you recently change tires? Gas stations? Tow something heavy? Too many variables to guess at

 

[Burla]

pump tires to high side of psi. So this is FACT, when my wife's tires were new we lost 2 mpg's for nearly a year, when they broke in we got the 2 mpg back. I even noted that a couple years ago in syn thread. New tires are real grippy, it takes more power to push them through the road.

Now, my wife went to a specialty tire super aggressive for the rain and she has a 4 cyl. If you went more aggressive this is an easy answer.

this from tirerack...

New Tires Generate More Rolling Resistance Than Worn TiresThe automotive industry estimates a 10% increase in tire rolling resistance equals a 1% to 2% decrease in vehicle fuel efficiency. So, drivers should expect a 2% to 4% decrease in mpg after installing new tires.

 

[neverhme]

I'm gonna go with Space Aliens. Yeah, that's the ticket. If you want a serious answer though, you need to provide more details, it is anyone's guess without knowing the details of ANYTHING about the picture you posted. Did you recently change tires? Gas stations? Tow something heavy? Too many variables to guess at

Yes as said new tires and the drop in K@N filter, gas same, same roads I travel.

 

[Black1500Ram]

Most likely the tires.. what were your prior tires? (HT, less aggressive AT’s?)

Edit* also that pic was taken at 20mph… you’ll never see good instantaneous mileage at city speeds.

 

[CanuckRam1313]

I'm going to say new tires, too!
When a tire is brand new the rolling resistance is greater, per se, then when they break in.

Caveat to this though, and albeit your rig is lower mileage, but a 2015 according to your sig... Have you taken off your throttle body and given it a good inspection and servicing lately?

Age can also affect things like performance and/or fuel economy even though mileage is lower overall.
PCV valve.... take it out and clean it.
Air filter?
Spark plugs... taken a few out to see their condition and gap check? Perhaps replace with NGK Ruthenium HX plugs?
Maybe a couple of bottles of Red Line SI-1 in the fuel tank and a fill with premium, plus a good highway spanking to clean things out?
What are your oil change intervals, and what oil and filter are you using?

 

[Ken226]

I got 14mph commuting to work with Atturo Trailblade 33 12.50 R20 mud terrain tires.

When I switched to Goodyear DuraTrac 305/55R20 all terrain, that dropped to 12.5 mpg.