i've been on amsoil 0w30 & 5w30 from 1O - 4Ok personally i feel that fc is not consistent & very irregular up & dwn... after travellin for abt 7k i feel the oil makes the engine abit sluggish too.
5Ok i tried FK massimo Ow2O eo its rather thin but as i dun loot my engine frequently so its still ok. FC wise very gd & maintained thru out the entire 1Ok of travellin.
6Ok i switched to KIC 5w3O so far so gd engine is still as smooth & quiet as before and i managed to obtained the best fc among all the brands i've tried.