H, Canterbury.

Don’t fill your fuel tank right up…driving around with a tank full of fuel your vehicle will weigh more which will reduce fuel economy.

[For the record, the average car holds about 55 litres of fuel, and 1 litre weighs about 0.71kg (but varies on type of petrol of temperature). So a full tank of petrol weighs about 40kg. – Oily Rag Ed’]