Recently had my "free" 2 yr. VW service @ dealer. Valvoline "MST" oil was used (assuming 5w-30). I came to the conclusion after a short period of use (around 200 mi.), that Castrol 0w-30 is a much better oil for my 2.5L. I drained out the Valvoline oil and put in a 5g. jug and planned to use to the 05' Focus. Anything to worry about doing so? BTW, after this short usage, the oil was pretty dark, which surprised me. Thanks, Bill.