Okay, the boring back story. I sent one of my crew (I'm new on the job) to buy ten quarts of 30-weight oil for the ranch Case tractor, since there was a half-full quart of SAE30 labeled "tractor" on the shop shelf. Oil filter on the Case was marked 2015. Figured it's overdue for an oil change, and I'd keep the tractor on the same diet, since it still runs great. The ND stuff he got from the store doesn't say "motor" or "engine," so I posted the thread. If the Case grew up on detergent oil, no harm with ND, since the oil is bought and paid for. If the Case grew up on ND oil, again no harm with ND. And I don't want to dissolve any old sludge, I just want to be sure that an oil that isn't labelled "motor" or "engine" will be okay in the crankcase, not made solely for non-motor applications.