i have been reading all these threads, and all it does is confuse me. trying to understand all the terminology..didn't know it was so complicated. one guy says this oil is real syn, the other guy says it isn't. my question.. i have a nissan sentra 02 2.5 4banger. manual says "Only oils with the AMERICAN PETROLEUM INSTITUTE (API) certification should be used. This type of oil supercedes the existing API SG SH or SJ and Energy conserving 1&11 categories..sae 5w30 is preferred for all temps. 10w30-10w40 visc oils may be used if ambient temp is above 0degf. i am in the above 0degf range going to high 90's. I WANT A FULL SYNTHETIC!! is the m1 full or not? which grade should i use? delvac is mobil? amsoil and shaeffer pretty much does not exist here. penzoil, castrol, mobil, quakerstate, are the ones that say "synthetic" that are available to me. please help. which one and which grade? i drive hard, mostly always close to red (6250)and i change oil at 3k kilometers, not miles (i think it's 2k or so miles..peace of mind. i don't mind the cost) car has 7,500 kilometers. thanks.