ARGH....
... if you have a digital 'clock' in one tractor and a tach rpm clock on the other, and it takes you 1 real hour to move a pile of sand.. then the tractor with the digital clock will show that you used 1 hour. In the tractor that uses the tach hours.. if they are rated for 1600 rom, and you ran at 1200 rpm, then the clock will show that you used 45 minutes.... why do you find that odd??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
You are using the tractor below it's rated rpm... I.E. the tractor manufacture has rated 'working' hours based on a set rpm.. you worked the tractor less than it's rated rpm.. thus the tractor has not 'worked as hard ( aged as much.. based on work level ). This probably is very usefull if you break it down on a cost vs life table.. where the 'working' hours will be more usefull than knowing how long the ignition key was on.
Soundguy