rpm's of cats operation.

I have never heard this before.Have heard many stories of Cat's that were hard to start or had bad pony motors that ran 24 hours a day,many of those hours at a slow idle to save fuel.The last such was a cousin in BC Canada was clearing brush with a older D7 and was told he had a job as long as the tractor would go that winter. So it ran for several mouths except for a quick oil change or two.There are other problems some time from to much idle time like wet stacking,but not bad for bearings.And of coarse are fine state has or at least proposed a law that equipment was not to idle more than 5 minutes.
Ray

thanks guys it didnt sound right . I have a 1910 buick with a big 314ci four cylinder motor thats got a long stroke motor that i show off with it will idel so slow you can see the fan slow down and speed up with each power stroke . and have been do that for years with no problems. when i run my d2 pulling disc's there is no way it lugging cause the throtte is very responsive when i rev it.[attachment=15505]drivers side motor.jpg[/attachment][attachment=15506]exhaust.jpg[/attachment]

There is nothing wrong with running the old machines at low idle for a short time if you need to, but they were designed to work with the throttle wide open, the only limitation is not making them lug too much was, if the engine is working too hard at a lugged down speed and the temperature gauge goes up too high, work in the next gear down for any easier life and better fuel economy.