Hi all recently I have had some problems with my 2013 Ram 2500 with the 5.7l Hemi. Traveling through the mountains(RPMs fluctuate with hills and acceleration) I averag around 23L/100km. But when i drive on flat prairie highways doing a 100km/h on cruise i will get around 30L/100km (consistent rpm around 1500 going in 6th gear). If i engage tow haul (draws out shifting point, more pressure in the transmission) i can average 18L/100km on a flat highway doing 100km/h at 2100 RPM. Or if i drop the truck into fourth gear doing 100km/h it will average around 21L/100km at 2500 RPM. (at low rpm it burns lots of fuel. at higher RPM it does better on fuel) Around town it does allright on fuel. I have spent 5k$ at the dealership getting the lifters done that did nothing. I have changed the spark plugs and O2 sensors are good. If anyone has an idea of why the truck burns so much fuel at a lower RPM cruising down the highway, it would be much appreciated.