John,
We're on the same page for the most part.I think that 6000hr in 30yrs is definitly streached out. I understand what you are saying about the difference between a tractor and truck, there will be variences as the tractor most likely has more work time. So if anything with theory, the life expectancy would be less. That being said, I dont buy that either, if all maintenance is equal....
In a diesel engine, everything introduced into it has lubricating properties(except the air /forums/images/graemlins/grin.gif). This is why I'm a big supporter of quality fuel that doesnt have a long storage time, MFG recomended oil change intervals along with a clean air filter when needed. The combustion process of a diesel is also less violent on the bearings because of the smooth steady burn it produces.
There are allot of OTR trucks out there with more than a million miles between overhauls.. Sometimes they are just overhauled because of time, not failures. These engines often are disassembled with the factory crosshatch in the cylinders(if they are taken care of). This leads me to believe my tractor given regular attention to maintenance should last a very long time...
Back to the 6k hrs in 30yrs. With my formula for truck hrs that would come out to about 6,500mi per year. This would dictate about 1 oil change per year(goes back to the original recomendation /forums/images/graemlins/smile.gif).. I dont recall from his post, but I dont think that was the interval(I may be wrong)... If the oil is changed regularly, there would be no need to send it for analysis.. But, if we streach that time and try to get the most out of it (syn or dino) we do need to have it checked. I dont fall into that category, thats why I made the comment that I dont test oil..
Sorry for the automotive comparisons. I've been a tech for the past 15yrs, the whole hour thing is relitively new to me.. When I look at it this way it makes sence to me...There are allot of similarities..... I dont want you guys to think I'm correcting you, I just expect my tractor to live about forever if I take care of it. Part of this is based on the fact that just about everyone around here has a running 8n(55+yrs old) /forums/images/graemlins/shocked.gif..