Originally Posted by def
If you suspect that your oilhead is running the oil hot, I would consider synthetic engine oil. Synthetics tolerate much higher oil temperatures than non-synthetics. The Noack score tell how various oils cook as temperatures are elevated. Oil cook-off leads to varnish and sludge as well as an increase in viscosity, all bad things.
Some oils foam thereby entraining air in the oil which leads to poor cooling and elevated temperatures.
Also, your oil filter may be bypassing oil. This could lead to variations in temperature.
Make sure that your engine internals are clean and varnish free. I have seen some air cooled engines that were badly varnished after a few thousand miles...the Ducati 620 comes to mind. If you suspect your engine is not pristine inside, run an additive...I like Rislone engine treatment. It will clean up a varnished engine.
Many of us boxer riders use Mobil1 15w-50 in our 1100s and 1150s but follow your MOMs recommendations regarding viscosity for your model.
620's run unbelievably hot. I do not understand why Ducati didn't fit a cooler on these bikes. They heat up and fast! I changed the oil on the wifes bike often because of this...