Hey all, I am new to BITOG. I own a 2002 Nissan Altima with the VQ35DE since 56k original miles and now has 72,000 miles. The engine is in excellent condition, I bought it from the original owner who was an elderly lady who saved her receipts for everything. As a young car enthusiast, I have since done full bolt ons and a tune to wake the car up. It is my daily driver. I have been using Mobil 1 5W30 and changing it every 3,000 miles. From the factory they recommend 5W30, or 10W30 and 10W40 if ambient temperature is a bit warmer. I live in Metro Detroit, so we have cold winters and hot summers. Because I drive fairly spirited (never abused, but I definitely do WOT at times and do some minor auto crossing, I am a bit worried that I should go thicker. Also, VQ35DE engines are known to be slightly thirsty for oil, plus they tend to run a bit hot from what I've heard (I have ordered an aluminum Mishimoto radiator to help).. so my question is, since Nissan's general fecommensarion is 5W30 but also put 10W30 and 10W40 as OK in the owners manual, wouldn't 5W40 technically be the best option even though it isn't stated in the owners manual? It would be a little thicker at warm temperatures offering better protection and less likely to shear down under spirited driving, but still have the thin 5 weight for cold starts in the winter. I'm told that many cars recommended visocities from the factory have to do with fuel economy also, which I don't care about. I want the best overall viscosity for a a balance of protection and performance, efficiency doesn't matter. My second question is, depending on what viscosity you recommend, what brand and model of oil should I go with? I'm sort of picky about staying on top of changing oil so I like to keep a 3,000 mile interval. Mobil 1 seems to have its lovers and haters, as well as Pennzoil Ultra Platinum and AMSOIL Signature, I'm just not sure which is best for me because people seem to be so opinionated on oil. Also, because I'm almost to 75,000 miles and have an older car would it be better to go with a "high mileage" type of oil? Any input and recommendations are greatly appreciated. Thanks!