Should I switch to synthetic....
Run what you want. No reason to be afraid of synthetic. I usually buy Pennzoil Platinum 5W30. Mobil 1 isn't bad. If you want a little more viscosity I would go with Mobil 1 High Mileage before I did something like go up to the wrong viscosity (like 40 weight or above).
I don't like BP so there is little chance I would go with Castrol.
Again, I have no experience in this area, just don't think something is bad just because it's advertised. What if all of these other better oils started a massive ad campaign? Would we automatically assume that they changed their formula, their product is now crap, and now the only way to sell it is with marketing? No, they probably just want to get the word out and sell more.
If you want to know more about Royal Purple, or any oil for that matter, try some place like bobistheoilguy and look for used oil analysis and reviews.



