I used to consistently be around 18 mph overall. Now I am lucky to get 15. Mileage while towing my boat has dropped to 12 when it used to be 15. Any idea's? Truck is stock, but has 185k on the odometer. Could it be transmission slip?
2004 Ram 2500 5.9 HO.

 

Could be a lot of things. Could be something simple like different tires, low tire pressure, or clogged air filter. My mileage always drops if I leave the air filter in too long.

Or something more complicated like a failing injector.

Start with the simple stuff first.

 

Poor fuel ?

 

The difference of driving at 55 mph and 75 mph can be 15% or more. Have you changed driving habits?

 

Driving the same. I got new tires, but same tread design. Filters are all good and nothing has changed. Truck seems to run fine and has as much power as ever. I am stumped.

 

Also depends where you live, winter fuel cuts down on your mileage too. clean air filter clean fuel filter helps mine thats for sure.

 

like said before, make sure your filters are clean, clean your sensors, could be bad fuel and you could run some cleaner through your fuel system