My '06 Silverado is my commuter, doing 15 miles of service daily during the week. Most weekends it sits, unless I am picking up some dirt/bark for the wife, or going to Home Depot. Right now it has about 23,500 miles on it, and I run an approximate 5K OCI, which works out to be once a year. Up until 20K, I ran dinos, either Quaker State or Castrol, depending on what was on sale. Then I decided that because of my short trips, maybe I should switch to synthetic. Went with M1 @ 20K. Now after checking out this forum, I am wondering if I should stick w/ synthetic or go back to dino. I don't tow or off-road; it is mostly rural streets to work. Probably later on this summer when it turns over 25K I will have a used oil analysis done. What do you folks think? Stay with M1 or go back to dinos?