I bought mine used but have never seen anything in mine and i have checked it everytime except this last change 9at 1130 pm the night before a 300+ mile ride).
I now have 30,000 km on my P250.
as to the OP... I have not really felt the need to go to a synthetic oil. The P250 has an oil change indicator and when I gets red, I buy a quart at Wal-Mart and change it. A straight oil change takes more time for set-up, draining, and clean-up than the actual work. I typically use the Delo or Rotella 15W40 as I understand diesel engine oils don't have the "gas-saving" additives in gas oils that don't work well in the high-temp m/c engines. I know the oil is dark when I change it every 2,000 km or so. CVT scooters do not have wet clutches like geared bikes and do not require the m/c specific oils some m/c require as the gas saving additives can ruin a wet clutch. I may be wrong , but this is what I have been doing and i am sure this is better care than many third world riders do for thier scoots.