Recently bought a new rx-8 and the previous owner would use royal purple oil I feel more comfortable using the 5-30 conventional from valvline I think is what is called would changing the type of oil and filter effect the car?

 

Congrats on the new 8! Oil is oil so no harm will happen if you want to change it out. I personally prefer conventional as well. Ideally try to use the Mazda oil filter though. Its only $8.