Westpac Extras offers. Get $5 cashback when you spend $50 or more on fuel and in-store at Caltex Star Mart locations. Only 1 cashback offer per merchant per cardholder. Offer is valid in store only. Available at Caltex Star Mart locations only.To be eligible, the qualifying transaction must be made by you or your additional cardholder on a card that is connected to your Westpac credit card account.