Hi there...I am a little peeved...I brought my newly acquired 2002 Subaru WRX Turbo Wagon in to Jiffy Lube for an oil change and since I had never been to one, was caught unaware when I was asked to choose an oil - reg, prem synthetic and then the "top of the line" stuff aka most expensive. Without any help from the "order taker/cashier", I chose the Premium Synthetic. I do not know what the previous owner used. Now, am I obligated to use this same oil each time I get an oil change or can I switch back to the regular, lease expensive stuff? Or is it good to alternate between the two? I don't want to harm the engine. I have heard conflicting info on whether Turbos benefit (or not) from using synthetic oil. Help! Thank you!!