Citi Cash Back Card would be the best. 8% cash back at food & beverage outlets, supermarkets, food & groceries delivery (including Deliveroo, honestbee, RedMart) and Grab rides globally. Up to 20.88% at Esso and Shell, and 8% Cash Back at other petrol stations.
Personally I go for SPC reward card with POSB everyday card. 10%+ 5% and 6% cash back on final amount. It's best when your area nearby got shengsiong.
Do you go for a particular brand of petrol? As different petrol brands actually ties up with different credit cards to give different discount. It also depends on what is main categories of your expediture to recommend the one that best suits your need.
You may want to refer to the link for reference and comparison: https://www.moneysmart.sg/credit-cards/petrol