From reading other UOA and comments by this knowledgeable membership I "think" Mobil 1 10w30 is the best solution for my OC needs, check out my rationale and let me know if I'm all wet. My vehicles 2004 Toyota 4runner with the 4.7 V8 - Currently 2000 miles. Changed oil at 1750 miles with dino Castrol GTX 5w30 and will go to Mobil 1 10w30 at 5000 miles. (Will then run a 5K mile OCI with Mobil 1 10w30). 2003 Nissan 350Z with the 3.5 V6 - Currently 6000 miles. Changed oil at 1200 miles and 4000 miles with dino Mobil drive clean 5w30 and will go to Mobil 1 10w30 at 7000 miles. (Will then run a 5-7K mile OCI using Mobil 1 10w30). Reason for Mobil 1 10w30 is great results on other similar engines, and it is easy to find in local stores. I feel I can use this oil year round in both vehicles, since Toyota and Nissan recommend 10w30 for temps down to "0" degrees. I live in SW Missouri and it seldom gets below "0" and if it does I would think that Mobil 1 10w30 would still lube just fine and not cause any damage to the engine. Both vehicles are kept in a heated garage. What do you guys think? Any other easy to find oil that you think would be better?