When we say 5/10-40 we mean a true fully synthetic as well, eg motul or redline. Possibly royal purple, I haven't done any reading on their oils though, can someone confirm?
Also I think it would be great if someone could edit the first post (admin) with a list of oils and their classification eg semi-synth fully-synth group IV etc.
edit: I've compiled some basic facts about oil ratings and a list of some of the common brands and their ratings, I'm going to report the first post and see if an admin can edit this information into it as I think it would help with a lot of the repeated questions. If there's anything that could be added or changed post it up.
When choosing oils the better the rating, generally the better the oil, and also the more expensive. Keep in mind even the Group II oils are probably still better then any oil that was made when your car was manufactured.
Basic explanation of ratings
Group I - mineral
Group II/II+ - hydrocrak (VI below 120)
Group III - hydrocrack (VI above 120, mineral derive "Fake Synthetic")
Group IV - polyalphaolefin (man made Synthetic)
Group V - Ester & other un-group fluid (Ester or Polyolester, super high grade Synthetic, good for aircraft jet engine).
Common products and their ratings.
Redline (Group V Polyester)
Motul 300V (Group V)
Motul 8100 E-Tech 0W40 (Group IV/V Blend)
Mobil 1 (Group IV)
Motul 8100 xcess 5w40 (Group IV) ~$59 - one of the best value
Castrol SynTec 0w30 (Group III)
Castrol Edge Sport 5w30 or 10w60 (Group III)
Motul 4100 Turbolight (Group II?)
Keep in mind that the 100% synthetic stickers mean jack, just means that the oil is at least Group III. As far as viscosity ratings go, this depends entirely on what temperature range your car is going to be used in and your driving style (track or street car) A decent read through this thread should help you answer that.
As far as oil filters go, get a genuine nissan one if you don't want to spend much, these are superior to ryco/cooper.