well, I was planning on having my oil changed tomorrow so I went to Walmart to get my oil as I have always done. When I get there they have no Valvoline synpower sythetic oil---none at all. so I was left with a dilema----- what do I switch to for this oil change, I know I need to stay with synthetic so I bought Castrol Sentec 10w30. I have never run Castrol but have heard that it was pretty good. any comments from the asylum about this? Need to make an oil change early in the morning since I plan on doing the dyno runs tomorrow.