Sport45 wrote:
Horsepower is horsepower. Two prime movers with the same HP will pull the same load up the same hill at the same speed. I don't care if it's gasoline, diesel, electricity, or steam powering them. Just let them operate at the speed they develope that power and ignore the sound they make.
Gasoline does loose some to diesel in thet more gear reduction can mean more parasitic losses and less HP delivered to the ground. The turbocharger also gives the diesel an advantage at higher elevations. the playing field may level if turbocharging becomes popular on larger displacement gasoline engines. A 5.0L ecoboost would be a good 3/4 and 1-ton truck engine for part time towing IMHO.
Sometimes the gasoline engine will win simply because the diesel can't spin fast enough to make the speed while delivering its extra torque to the ground.
Diesel will almost always win the fuel efficiency award. Whether or not it saves enough fuel to pay for itself has to be determined on a case by case basis.
Horsepower is horsepower but you need to look at the torque curve and consider the transmission ratios to have any idea how the truck is going to pull a trailer up a hill. My Ford which has a very flat torque curve will only make max HP at one rpm which means one speed per gear: 21 mph in 1st; 35 mph in 2nd; 54 mph in 3rd; 72 mph in 4th. A gasoline engine which makes its max HP at 4200 rpm (and likely also has a fairly flat torque curve) with the same transmission and rear axle would really only have 2 usable hill climbing speeds: 1st gear at 30 mph or 2nd gear at 51 mph. A highway tractor with a large Cat and an 18 speed transmission will have no problem putting max power to the wheels at any speed. (the big Cat has a torque curve which drops significantly as the engine rpm increases)
