It's a very complicated promotion too, sounding like it would cost a fair bit to get everything.
Wave 1 - June 7th to July 16th - Four Transformers Movie Tumblers (Optimus, Bumblebee, Sqweeks, Megatron).
Stamp issue period: June 7th to July 16th
Redemption period: June 16th to July 16th
Earn one stamp for every HK$200 (about AU$35) of Caltex gasoline you purchase. Collect six stamps (about AU$210 of fuel during those six weeks) to redeem a Caltex “Exclusive Movie Tumbler” for free.
(total cost would be about AU$840 of fuel to collect all four)
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Wave 2 - July 17th to August 29th - Transformers Tissue Box and Talking Heads (Optimus & Bumblebee)
Fuel up for HK$500 (about AU$90) or more of Caltex gasoline to get the Exclusive Movie Box of Tissues for free.
Or
Earn one stamp for every HK$200 (about AU$35) of Caltex gasoline you purchase. Collect four stamps to redeem a Caltex “Exclusive Movie Talking Head Figure” for an additional HK$49 (about AU$9). (total cost would be about AU$149)
To get all seven exclusive items, it would cost about AU$1079, with $1070 of that being fuel purchases during those two months.
That might be possible if you are a delivery driver or have a big commute to work, but HK is a small place, so unless you have friends giving you their stamps, this could be difficult to do.