regular mobil 1 5w-30 is a TRUE synthetic, if you don't believe me check out their website, they break down every class of oil and advertised oil. I personally used it for 21k on my z and no problems. The only difference between Nissans oil and Mobil 1 is the fact that the nissan oil has ester in it. Also Redline is a Ester based oil. So IMHO i think some guys on here are getting confused with the fact that Ester makes the car run quieter than mobil one or any other non ester based oil. I run 5k on my oil because 99.5% of my driving is just highway miles and no stop and go traffic. The more stop and go traffic you have the more often you should change your oil. Buying any oil at walmart will save you atleast 5-10 bucks rather than buying it at a parts warehouse, but buy the filters from there. Mobil 1 has some good filters out there, or K&N
thres my 2cents worth