The full-tank method, step by step
- Fill up until the nozzle clicks off and reset the trip meter (or note the odometer).
- Drive normally until the next fill-up.
- Fill up again and note how many litres went in.
- Consumption = litres added ÷ kilometres driven × 100.
Example
You drove 620 km and 41 litres went in: 41 ÷ 620 × 100 = 6.6 litres per 100 km. At today's average petrol price (9.52 RON/litre), that is 62.83 RON per 100 km, or 0.63 RON per kilometre.
Repeat over two or three fill-ups: their average is more accurate than a single tank.
Why it differs from the official figure
Official values are measured in a laboratory on a standard cycle. Real traffic adds speed, congestion, temperature, air conditioning, load and tyre pressure.