I usually buy my own oil & bring it to my workshop for routine service. I have been a big fan of Mobil 1 for a longtime.
This has to be the best deal in town to purchase motor oils. It's called Forklift Enterprise at 15 Teck Chye Terrace. It's diagonally opposite our durian haunt in Upp S'goon.
Mobil 1 Gold is only $80 for a 4 lit pack. Esso is retailing It at $117. There's Castro Edge, Shell & others...this shop sells oil & grease only. Go check it out. Tel 62886701.