Hi Scotty. My Nissan has just over 100k on the odometer. I’ve been using Castrol GTX 10-30 weight oil; I always change my own, and I always use Wix oil filters around 4K mile intervals. The owners manual indicates that only mineral based oil should be used, and that synthetic oils are not to be used. Recently I decided to tempt fate and changed my oil using Castrol’s synthetic oil, and the engine sounds like it is running better. What possible reason could Nissan have for recommending against synthetic oil?
Strange. I thought "synthetic" oil came out of the ground too.
Correct, all synthetics start out as highly refined crude oil.
Your owner's manual specifies 5w30 oil for most situations. It does not say "only" conventional oil, it says it recommends is but doesn't require it. Technical & Consumer Information 9-5.
