Other answers in blue. I should also mention that rpm's don't necessary negate to HP with a diesel. You can run 3,000 rpm's and produce very little Horsepower. But as long as your not loading the diesel you also will not get any heat production or horsepower gain, simply because unlike a gas motor if you raise the rpm's up your mostly free wheeling off the motors ability to self ignite. For example, in the winter i can High idle my truck at 1,200RPM's all day long and not see the engine coolant warm up for anything, But switching to 3 cylinder High idle will put a load on the motor about 17% to be exact, that means the engine will warm up. With EB on and 3 cylinder high idle i can load up to 30% on the motor. Conversely, on 6 cylinder high idle, with 0-1% load i'll burn about 1 gallon an hour. but on 3 cylinder high idle i'll burn 2-2.5GPH, and with my Exhaust break on with 3 cylinder high idle a whopping 4.5GPH. This is all at 1,200RPM's, but as you can see the gallon usage went up considerably, as i increased the load on the motor. diesels are a different animal from gassers.