EVIL TWIN

Is that you Richard? How can the second number indicate the viscosity when hot? If that were the case, you're saying the viscosity becomes higher when it gets hot, ie it becomes thicker when it gets hot. I'm pretty sure oil becomes less viscous when it's hot. "the protection of a 50W oil" simply means a higher level of wear protection. I may have confused the explanation, as I was just regurgetating what was written on the back of an oil container. What I meant was a 5W50 is thinner than a 10W40 but offers higher protection from wear.

Keep in mind guys, when the RB family of engines were designed in the 80's, synthetic oil wasn't terribly common. They were designed to use a 7.5W-30 mineral oil. Use this as a minimum and anything better will just be a bonus. I've tried the Nissan 7.5W-30 and it's pretty crap compared to pretty much all non-mineral oils. With the numbers though, the first number (eg 5W) is the weight or viscosity of the oil - the higher the number, the thicker it is. Thicker oils offer greater protection but don't flow around your engine very well, which is where the second number comes in. The second number (eg 50) represents the amount of protection it offers - ie the protection of a 50W oil. So the ideal situation is to have a thin oil that will flow easily to cover every component as quickly as possible, but have the highest protection. You don't want to go too thin though like 0W which may actually drain down while sitting at the traffic lights quicker than your idling engine can get the oil up to the top. I personally use Mobil 1 or Penzoil 5W-50 in my GTR. Probably not entirely neccesary, but I'm not taking any chances - I want the best for my baby

More than likely - the City West licencing centre? I was picking up my plates last month. That sticker was on the car when it came from Japan. It has "GTR Magazine" on it, so it must have been a give-away in Japan.

I've got EVIL TWIN In case that doesn't make sense, they're on my GTR