a 10w30. As we know the 5w is still too thick from reading the previously posted article...Motor Oil 101. The problem was the conventional oils back in the 1990's had to have a lot of viscosity index improvers to get the oil to thicken less as it cools down to the 5w thickness. This is not a problem with today's synthetic oils. It's also why a lot of people still buy 15w50 oils. Years ago you could buy 10w40, but to get a 50 operating weight oil it was 15w50 so the VII's were not excessive. This is better explained in chapter 2 of Motor Oil 101. The bottom line is the Nissan TSB is obsolete.