ok guys, im coming up on 10000 mi, so im debating between the gtx 5w20 and the mobil 1 0w20. I already have the castrol gtx 5w20 in there with a bosch prem filter, and its holding up very well, but, im wondering if i can do better. Im not in stop and go traffic that often, maybe 15 min of the day, and most of my mileage on the weekends is highway. Only real rough driving i do is usually once a day, i rev my honda civic up to about 6000 rpms in 3rd to 4th usually to get my daily speed satisfaction. Cost isn't really an issue, but im still waiting to see any mobil 1 0w20 quarts around walmart. What oil would be the best for protection and how often should i change it?