To be honest I don't think it really matters. I would like to see any proof that it does. Our tractors are stopped, started, stalled, etc. in all rpm's, throttle positions, conditions, etc. We have never had problems with tractors and all of the tractors I can remember that we've had have all gone thousands of hours before any major work. Basically just start them up and put the idle at a slow speed. Idle them down and shut them off.