I too have the oil thermostat for my 912uls with 750 hours on it now. It seems, as Scott said, that it doesn't help much on cold warm-up. It seems like it did a better job when it was much newer. I am wondering if the little thermal element in the stat has failed, maybe yours too Scott, and it should be replaced. I know on cars that element seems to have a limited life. Any ideas on how to test it without disassembly?