@andycupra thanks for the reply. My engine is 60hp, 1 litre petrol, non turbo, 3 cylinder. The official figures for the 60hp 1 litre engine are 55-59 city, 72-74 highway, 66 combined. I take these with a pinch of salt, but 45 combined is surely pushing it. MPG source here.
My old VW Up! (move...