Use Citibank Dividend Platinum card when you pump Esso.
Eg. You pump $100, you pay $95 based on 5% station discount.
End of the month, you will have 8% of the $95 credited into your Citibank cashback, that is $7.60.
So you actually pay only $87.40 when you pump $100. As good as a 12.6% discount.