Do the manuals stipulate a specific oil type, eg synthetic? How many quarts do they hold? I know in automotive applications that synthetic oils, along with greater capacity oil pans allow for greater time between PM's.

every mfg has its own recommended oil change interval.
most of the trucks i've done in the past used to be an average of around 200 to 250 hrs. Since the technology has improved drastically over the past few years some mfg's have increased thier recommended oil change intervals in some cases. I've seen some go as far as 500 hrs.

You just need to check with your dealership and see what the recommended interval is by mfg's recommended specs based on the truck you are servicing.

Of course as was mentioned, the envrionment plays a part in this as well, normal conditions you would just follow the recommended intervals. Harsh or heavy use environments of course you would monitor the oil condition and change the interval based on that.

Hmmm.. I do PMs on trucks that run 24/7 and they log 100 hours a week. The manuals for newer Cats, Hysters, Yales said oil change every 250 hours. I let those go for 400 hours between changes.

Every manual I've read always puts Pm's between 100 to 150 hrs of service. The best answer to this I found on another thread on this site- it has to do with the engine revolutions per hour of usage. The total revolutions in 100 hours equals the revolutions in an automotive application in 3000 miles. The PM schedule always seemed alittle much to me until I saw it explained that way.

Each truck is diffrent as is every working enviroment...depends on how hard they are used and how much abuse they go thru...some people say follow the maintenance service guidelines in the trucks operators/service manual but this is just a generalized guideline....if the truck is used very little then the time frame can be extended but if it is heavily used then that time frame will be shorter