Volkswagen AG in Hamburg, made the most economical car in the world with an engine capacity of 1-litre, powered by diesel. It consumes just 0.99 litre per 100 KM. Apparently, the top speed is 75Km/hr.
To give you an idea on the economy, it cost less than 2 cents per km or less than 30 cents from Lutong to Miri.
More information here. Or search google.