ORIGINAL: miniman
Far better to use the best oil you can get, add a little more at the start, then as the motor settles in reduce the oil to the optimum level. This will give you a motor that will last for years giving great performance, flight after flight.
Everyone has his/her own methods and most will work out fine. But if you want to squeeze each and every ounce out of your engine, a break-in period on mineral oil is the best way in my opinion. My DL does 7900rpm on a Vess 22A. I have 3/4 gallons Lawnboy Ashless 32:1 mix left, think I'm gonna feed that to my Volvo and bolt the Vess 23B on tomorrow
I have 2 gallons Amsoil Saber 80:1 ready. Will post some results.
And if you're concerned about any chemical reactions between the mineral and your preferred synthetic oil, simply mix a drop of each and let it sit overnight.