Stop and go traffic for me during L.A. rush hour. Stuck in the 405 Freeway for at least a couple of hours to and from work, five days a week. At night or during the weekends, or when traffic clears, I'm doing at least 80 mph, sometimes even more, to get to where I want to be. It's hot during the summers and mostly warm the rest of the year here, with some rainy season. I also drive it to Las Vegas, San Diego, San Francisco and anywhere else in between on occasional trips.

I had 5w 30 regular oil originally, now using 15w 40 as I've mentioned. Now, contemplating on using Mobil 10w 30 synthetic year round with 3-4k interval.

BTW, I did purchase 12 quarts of Amsoil 5w 30. Thinking about trying that first instead of using it as ingredient to my home-brew synthetic blend for my brother's S90. We'll see.