Shell Rotella 5w-40 Synthetic in WRX, 10w-30 Mobil 1 Extended Performance Synthetic in GSR, 5w-20 Mobil 1 Extended Performance synthetic in the Accord, and 10w-30 Castrol GTX in Malibu (which is garbage....car was running harsh and that's just normal driving...going back to Synthetic...i will be trying different ones).![]()