I don't know how long till they up their price like everyone else. It's probably only worth checking, if you will be passing them soon (and not going out of your way to get there)
If you are passing the Blackburn South area, I just filled up some unleaded petrol at $1.36 per litre at
United Petrol
112-124 Middleborough Road
Blackburn South, Victoria 3130
Note: I've never used them before, but since the others hiked their prices up to $1.50+ today, I thought I'd give this station a try.
Note: That was the price at 10:11pm