Repco engine oil sale - Mobile 1, Shell, Valvoline and Castrol are pretty cheap + possible 20% off
The ones that caught my eye -
Valvoline XLD premium 5 litre - Repco price $19.99 - elsewhere $24
Shell Helix HX5 - Repco price 5 litre $19.99 - elsewhere $27.95
Castrol Magnatec 15W-40 5 litre - Repco price $29.99 elsewhere $43
Mobile 1 5W-50 5 litre - Repco price $49.99 - elsewhere $71.50
You can also join the Repco email list to receive 20% off your next purchase although I suspect that the terms and conditions of the discount will be that it only applies to full priced items - if thats the case then you still get the 20% off for another day.