Simple - Buy 2 cases of certain stubbie-sized bottles, and get 30c off per litre petrol at Coles Express.
Choose from Cascade Light, VB, Stella Artois, Carlsberg, Victoria Pale Lager, Asahi Super Dry, Corona or Matilda Bay Fat Yak.
You get a special 22c voucher which must be stamped and presented at the same time as your "standard" 8c/litre discount thingy off the bottom of the receipt.
1 voucher + receipt per fuel purchase, max 150 litres. Included LPG and Diesel. Must redeem before 1st January 2012.
I grabbed VB at $38 and Corona at $50, as they were both on special today and therefore pretty reasonably priced. The other prices brands didn't seem very cheap to me, but stil might work out OK for you.
Filling our Falcon will use about 80 litres, so that's $24 off. Of course (as JV pointed out below), the normal discount voucher is 4c/lt and until 31st Dec they are offering 8c/lt… so the additional saving is actually less than 30c. Anyway, it's certainly worth it, especially if you are buying beer anyway (just stick to the on-special stuff).
There's a bit of fine print on the voucher, so here's a pic which shows the TOS and a few excluded Liquourland/Coles branches…
http://upload.ozbargain.com/2011/12/18/7430_30_cents_tos.jpg
It's pretty big 2592x1930 pixels, 627KB, you'll need to zoom it to read the fine print.
[NOTE - I have edited this post a couple of times to add more info]
team this up with your $15 liquorland voucher from the $15 case of beer fiasco and you're on a winner ;) Shame i used mine yesterday towards a case of coronas.