your bearing clearances dictates your oil weight,

 

I used Royal Purple Synthetic 5W-30, is it bad If I switch to Shell Rotella T15 15W-40 even tho is not synthetic? Reason I ask is because I heard once you go synthetic you can not add regular oil no more.
I kind of like the valve terrain noise, because I can hardly hear the lope of the cam even with an e-cutout right after the 3" downpipe... It only sounds choppy for the first 5sec from a cold start
Cam specs: Lunati 216/220 .560/.560 @114lsa W/ lunati dual springs.