 Some engines use a vaporizer, which uses heat from the exhaust manifold to vaporize the fuel entering the intake system.Petrol-paraffin engines were traditionally found in motor boats, fishing vessels, small tractors, light railway locomotives, and stationary auxiliary engines, but not in cars or motorcycles.The Milnes-Daimler motor bus of 1904 (based on the Cannstatt Daimler lorry), operated in London by Thomas Tilling, ran on either petrol or paraffin, but for starting the engine, or frequent stop-start work, petrol continuously was the preferable option.