Understanding Your Car's Fuel Consumption
What does 'litres per 100km' mean? How do you work out your car's real fuel usage? Here is a simple explanation.
Key Takeaways
- Fuel consumption is measured in litres per 100 kilometres (L/100km)
- Lower number = less fuel = cheaper to run
- Your car's real consumption is usually higher than what the brochure says
- You can calculate it yourself with a full tank and trip meter
- City driving uses more fuel than highway driving
What is litres per 100km?
This is how we measure fuel consumption in South Africa. It means: how many litres of fuel your car uses to drive 100 kilometres. A car that uses 7 L/100km needs 7 litres of fuel to go 100km. A car that uses 12 L/100km needs 12 litres for the same distance.
- L/100km = litres of fuel used per 100 kilometres
- Lower number = more fuel efficient = cheaper
- 5-7 L/100km = very efficient (small cars)
- 8-10 L/100km = average (sedans, small SUVs)
- 11-15 L/100km = heavy (large SUVs, bakkies)
How to calculate your real consumption
Here is a simple method anyone can do: Fill your tank completely. Reset your trip meter to zero. Drive normally until you need fuel again. Fill up again and note how many litres it took. Divide litres by kilometres, then multiply by 100.
- Step 1: Fill tank completely
- Step 2: Reset trip meter to 0
- Step 3: Drive normally until you need fuel
- Step 4: Fill up and note the litres
- Step 5: Litres ÷ km × 100 = your L/100km
- Example: 45 litres ÷ 500km × 100 = 9.0 L/100km
Why is my real consumption higher than the brochure?
Car manufacturers test fuel consumption in a laboratory under perfect conditions. Real-world driving includes traffic, hills, air conditioning, and different speeds. Your actual consumption is usually 10-30% higher than the manufacturer's claim.
- Lab tests use perfect conditions
- Real driving has traffic, hills, wind
- Air conditioning adds 5-10% more fuel use
- City driving uses more than highway
- Expect 10-30% more than the brochure says
What affects fuel consumption?
Many things affect how much fuel your car uses. Driving speed is the biggest factor. Other factors include tyre pressure, weight in the car, air conditioning, driving style (aggressive vs smooth), and whether you are in traffic or on an open road.
- Speed: faster = more fuel (especially above 120 km/h)
- Traffic: stop-start uses much more fuel
- Tyres: low pressure = more fuel
- Weight: heavier car = more fuel
- Air con: adds 5-10% fuel use
- Driving style: aggressive acceleration wastes fuel
Ready to see your own numbers?
Use the Fuel Cost Calculator