Penrite 10W-40 Full Synthetic Engine Oil (4L) is on sale. Pretty close to the low price the last time this was posted. Petrol may have gone up but at least you can still get some decently priced engine oil.
Repco is selling the 6 Litre for $62 or $16.50 for 1l.
Also this is other oil deal is part of the same sale: Castrol Edge 5W-30 5L Engine Oil $50.99 (Limit 2) @ Supercheap Auto ($43.34 via Pricematch at Mitre 10)