Yes, the 30c off was a buyers' dream, if you ignored the slight price rises- just a few cents on dozens of groceries - at both majors...

However, we generally needed to stock up...
Never tried to mix-n-match with a docket. Always needed the full 150 litres allowed for Girt alone. If necessary, we filled Jim's paltry 45 litre tank with a second docket.
If there was a 'Buy two Magnum ice creams for an extra 4c/l off', we'd take it up, as the discount - as already mentioned - effectively gave us the ice creams and a newspaper for free!
