Well, I'm about to change out the current Castrol GTX 5w20 on my wifes car. Its an 06 Hyundai Accent with a 3.5 quart sump. Its been ran for 5300 miles. I know that without a UOA I can't make a judgement about it, but its still fairly clean to the naked eye and there are no funny smells either. Gonna dump it and refill with some Valvoline Synpower that I got a BOGO on last year. I have to say that the GTX seems like a fine oil for the most part. All miles on the last OCI were 100% in town, stop and go. She refuses to drive on the highways down here. Any thoughts on the GTX in a 5w20? Oh yeah, I also use an OEM oil filter as well. Thanks.