Diesel vs gas......................

Hannibal wrote:
5200rpm for 100k miles? Why? Even with my lethargic 5.4L, I only occasionally turn 3800-4200rpm on the uphills. Easily less than 1% of our travels. Also, using gear reduction takes the load off of the engine by the percent of the gear ratio so although the engine is running at higher rpm well below it's peak hp rpm, it's doing less work letting gear reduction take the load. Like 2:1 rope and tackle to lift a load. You might have to pull the rope twice as many times but, it will require half the effort on each pull. As for the 5200rpm wearing an engine out, during R&D, Chrysler ran the 5.7L Hemi 300 hours at peak hp rpm full load. Upon dissection, it showed only normal wear and nothing broke or melted. The Cummins can also be run full load at peak hp rpm for hundreds of hours with no ill affects. Loading at low rpm puts more load on the lower end bearings. It's not "easier" on the engine as your ears might suggest.

I'm sorry about the 5200 RPM's. I just used that number because it was in a previous post. The way that I look at this is that when a motor is turning 4200 rpm's then it is turning 2X's what I'm turning at 2100 rpms. That's 2X's the wear any way you look at it. When you are turning that 4200 in your truck your torque converter is unlocked and that is a lot of wear on the trans and parts also. You say they test the Hemi for 300 hrs? That's only 18,000 miles at a 60 MPH average. At 40 MPH average (which is more realistic for a vehicle)it's only been tested for 10,000 miles. Now I know you are thinking that you don't run your motor under full power all the time but you would be surprised at how much you do. You don't have to put your foot on the floor to put full power out.