I just recently bought a 1989 Mazda RX7, 2D convertible (Second Generation) (13B INJECTION) brand new to this. I did some research on Wikipedia and got alot of info on the vehicle. I recently got an oil change and switch over to synthetic and i think the brand they used S/S synthetic PZL 5W30. As I was reading here one of the guys here recommended not using synthetic, but if you do us synthetic use Royal Purple. Can you tell me more about the Royal Purple please, do you think I should go back to regular oil to be safe.