my IAFM preve executive only getting around 200-220km for RM50 , city driving!! how do you get 300-350km for RM50 city driving??

i just did my first 1000km service only..

Before the 1st service, i went on highway drive from KL to Johor and back, had to pump RM100 petrol for the whole journey (rm50 each time before departure)
Was driving around 140-160kmh from KL > Johor . Coming back time around 100-120kmh Johor > KL .

Something wrong with my preve FC ?