Sythentic is good to use. But is there much of a difference between Castrol synthetic, mobil 1, and royal purple? Im not totally convinced there is. Personally i use mobil 1 and it works fine for me. Really the only gain you get from sythetic is that it will last longer than the conventional oil. If you use regular oil and change it every 2500 your not gonna hurt your engine at all. Ive kinda been leaning toward switching to regular because with my older car the sythetic has a tendany to get though the seals easier because of its viscocity properties. Youmight gain a small hp, like 3hp or something over the conventional.

 

i went from royal purple to castrol full syn and i felt a difference i dunno

 

Good or bad?