There are several ways to measure fuel consumption without an onboard computer. I used this method:
1. When the low fuel indicator lights up, I fill up to a full tank (the volume is shown on the receipt).
2. I reset the odometer.
3. I drive until the light comes on again.
4. I divide the number of liters filled by the distance in hundreds of kilometers: 40 liters / 3 hundreds = 13.33 liters per 100 km.
This method also works with a partial fill, but with a full tank the error is smaller.
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