EFFICIENCY DRIVE

Blokes banging on about how efficient the engines of their new cars are can be well wide of the mark. Even modern petrol engines struggle to top 20 or 25 per cent thermal efficiency. Diesels can achieve roughly 40 per cent and a new petrol engine design from Toyota in 2014 achieved 38 per cent thermal efficiency. But get this, way back in 1946, the PS Waverley paddle-boat used an engine that was good for 35 per cent efficiency as it splashed between various bits of Scotland. And what sort of engine did it have? A triple-expansion steam engine. Save that one for the pub.