Posted as an affiliate as I work at BNZ, but not related to this post - let me know if I need to change anything.
Using BNZ's Platinum card and choosing Flybuys rewards, and converting the Flybuys to Fuel discounts for Z/Caltex, you can get $1 off petrol at Z/Caltex for every $40 you spend on the card (works for a minimum of $60 spend = $1.50), which I believe is the best credit card reward earn rate in the market. Especially topical now with the price of petrol.
Earn rate = 1 Flybuys point for every $15 spent
Receive 4 Flybuys points by spending $60 (4 * $15)
Flybuys Fuel Rewards Conversion rate = 3 cents per litre discount for every 4 Flybuys points
Spending on fuel = using max 50L fill, 3 cents per litre is worth $1.50 ($0.03 * 50)
In above example, spending $60 gets you $1.50 fuel discount (or equivalent to $1 fuel discount for $40 spend). Works best by filling up 50L at a time to maximise fuel discount.
Account fee is $90 per year (charged half yearly), so you would need to spend $3,600 per year to cover that in fuel discounts, and make the most of the other features (the included travel insurance looks like it includes cover for COVID-19 which is a massive bonus if travelling).
It is good but u need a large enough car with 50L+ capacity to utilise it fully, or get 2 cars to fill each time, which I tried for a while but too much hassle.