I guess I'm lucky cause the guys at my dealership really know thier stuff. I have a really good relationship with them.

Had a dealer in colorado tell me the 370z must use the nissan ester or it
would void my warranty-went down and shoved my owners manual at him
and told him to show me where it said that. Then he apologized and said
well maybe it just recommended, but does not void warranty-i had them
put in my castrol syntec edge.

im a royal purple fan myself. but all in all there is VERY little difference in all the major oil companies from mobil1 to castrol to penzoil,

a 5w30 synthectic is a 5w30 synthetic no matter the brand and there will be minimal gains or losses between all of them. dont buy into the snake oil crap from nissan.

I'm giving my dealler a bottle of Royal Purple to use for the first service, they've absolutely guaranteed that the warranty will not be void if the oil weight is 5w30 and API certified at the correct grade =)

my dealership lolled their arses of when I told them that some dealers say that you have to use nissan's ester oil or it will void the warranty