I have used synthetic but honestly for the price you will pay for each oil change it wasn't worth it for me, I didn't notice a difference in smoothness or power or any of that crap, just price. I have always been a fan of Kendall Motor oil, it is a non synthetic oil that protects and last. and is about $2 dollars cheaper than royal purple. Basically just stay away from cheap non synthetic oil, like pens-oil or mobile 1 or any gas station name brand stuff. Also I always use 10w40 in my hondas unless its winter time then maybe 10/30