Total amount of petrol pumped at SPC station (meter reading): $250 / month
Using SPC&U card and pay by cash, current discount is 10% (promotional). Therefore $225/mth
Using SPC&U card and pay by POSB c/c, discount is 10% + 5% + 6%rebate, working out to about $200/mth, a further savings of $25/mth or $300p.a.
In photography terms, that's almost 1 x AF-S 35mm f/1.8DX, or much more than an AFD 50mm f/1.8