I realize there is another thread about a Versa, but I didn't want to derail that one so I'm starting my own. I have the 1.8L version (MR18DE). I'm not sure what everyone else has, but in that other thread I saw that most Versa owners are using 5w-30, which is what the manual calls for. Currently I'm using the German Castrol 0w-30 because of what I read about it. It costs the same as other major brand synthetics in 5w-30, so I figured why not. I've also read about the 5w-30s shearing to a 20w, and the GC 0w-30 would theoretically provide better start up protection; hence my decision to use the GC. Is this a wise decision? My car sees high RPM (4k+) occasionally for highway merging/passing, frequent traffic jams, and a temperature range of 10F to 100F.