Personally, I think 5w oil is too thin. As soon as it heats up its goin to get thinner than 5w. The oil will heat up quick especially if your tappin the limiter. Nissan probably recommends 5w for a stock vehicle in Japan, but over here the weather is hotter and there is not a whole lot of us running stock engines. I run 20w mineral synthetic blend and a few mates with tougher engines run 15w and 20w. They have 400hp v8s, a couple RB's and a SR pushing out 300kw at the wheels. The only engine failure I have seen from them is a rod through the block on a mates 383 chev while he was laying a skid at 8000rpm.
Anyway my 2c.