I gathered this off of the web. It talks conciderably about the
zinc contents in the new oils being too low. Claims that these are as high as .16 so should be good for older engines.
Castrol RX Super 15W40
Chevron Delo 400 15W40
Mobil Delvac 1300 Super 15-40
Penzoil Long life 15W40
Shell Rotella-T 15W40 one of the highest
Super Tech 2000 (WalMart) 15-40 next highest
Valvoline All Fleet 15W40
Castrol Syntec Blend Truck and 4X4 15W40