Type of oil

[Will12]

99 1.8T passat. I am using 5w 30 Castrol oil regular. I have been advised recently to use synthetic oil because the molecules are smaller in synthetic. Should I change type of oil next time, or is is O.K. to keep using same oil; and if I change, what do I need to do with the engine because as I understand, the two oils are incompatible (i.e. flush it, run with automatic transmision oil for couple days, etc.)?

[Will12]

I read on other forums that is better to use synthetic, and also they say it's not necessary to flush the engine, but I heard from my mechanic that it good to drive with quart of transmission oil two days prior to oil change. It seems like it removes sludge from engine. Anyone advises?

[Roadandguitarman]

Originally Posted by Will12

99 1.8T passat. I am using 5w 30 Castrol oil regular. I have been advised recently to use synthetic oil because the molecules are smaller in synthetic. Should I change type of oil next time, or is is O.K. to keep using same oil; and if I change, what do I need to do with the engine because as I understand, the two oils are incompatible (i.e. flush it, run with automatic transmision oil for couple days, etc.)?

I'm curious; why do you use 5W-30?

[Will12]

Low weight--good for small engines. And synthetic so it goes into small holes and has high breakdown temperature--good for turbo.

[turtlecrxsi]

5w-30 Castrol full synthetic.