FILL UP YOUR CAR OR BIKE IN THE EARLY MORNING WHEN THE GROUND TEMPERATURE IS STILL COLD.
Remember that all service stations have their storage tanks buried below ground. The colder the ground, the denser the fuel, when it gets warmer petrol expands, so buying in the afternoon or in the evening, your litre is not exactly a litre. In the petroleum business, the specific gravity and the temperature of the petrol, diesel and jet fuel, ethanol and other petroleum products play an important role. A 1degree rise in temperature is a big deal for this business. But the service stations do not have temperature compensation at the pumps.
ONE OF THE MOST IMPORTANT TIPS IS TO FILL UP WHEN YOUR TANK IS HALF FULL.
The reason for this is, the more fuel you have in your tank, the less air occupying its empty space. Petrol evaporates faster than you can imagine. Petroleum storage tanks have an internal floating roof. This roof serves as zero clearance between the petrol and the atmosphere, so it minimizes the evaporation.
IF THERE IS A FUEL TRUCK PUMPING INTO THE STORAGE TANKS, WHEN YOU STOP TO BUY, DO NOT FILL UP.
Most likely the petrol/diesel is being stirred up as the fuel is being delivered, and you might pick up some of the dirt that normally settles on the bottom.