I'm running Castrol Synthetic Blend 10W-30 right now and my car is running better than ever. Of course that may also be attributed to new bosh plugs, ford racing wires and running fuel and injector cleaner treatments. Does anyone know the usefullness/uselessness of using the blend and 10W-30 as opposed to 5W-30. Basically, I'll be changing my oil in a couple weeks at 100K and I would like to know what kind of oil i should put. At Hot Import Nights, I saw alot of people buying Valvoline Synthetic...is that better than Mobil 1? thanks alot guys

96 Contour LX V6
red ext. with tan leather int.
All options except ABS(who needs brakes anyway)
Bosh+4 plugs and 9mm Ford Racing wires
OBX racing intake
Aerospeed DTM style muffler with 2.25 custom catback piping - no res
BAT struts
Ground Control Coilovers
OMP strut bar