Hello, I'm new here and just have really one question I hope someone can answer or give their opinion on. I have a 2001 Cobra with a 2003 Mach1 engine. I know the 4.6 4v was originally spec'd for 5w30 before Ford moved to 5w20 to meet CAFE standards, so I plan to run a 0w or 5w30 in it. The original owner ran 5w20 Motorcraft SynthBlend with a Motorcraft filter. I plan to keep the FL-820S filter due to it seems to have nice reviews and lower cost compared to other like Royal Purple and K&N. I am still undecided on what oil to use though and have a small list of brands I would like some opinions on. If it matter the car is a daily driver, currently 17.5k on the engine, and sees occasional autocross, and drag strip use (5x's or so a year), I plan to do oil changes every 5-7k when I'm not going to the track. 0w30 Mobil1 0w30 German formulated Castrol (I hear this might be closer to a 40 though ?, and the most expensive in the list) 5w30 Motorcraft Full Synthetic 5w30 Motorcraft SynthBlend Also how are Valvolines Synthetics? If I remember right they were getting knocked on a few years back.