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Digger (Invercargill RSA), Issue 18, 16 July 1920, Page 14

The question of fuel economy is of vital interest to the users of cars, both because of its affecting, as it does, the pocketbook, and the ability of the car to cover great distances on a moderate load of fuel. A survey of this field by Dr T. Blackwood Murray, president of the Institution of Engineers (Scotland) shows that the brake thermal efficiencies of the various types of engines place this automobile motor in a "fairly satisfactory position." The locoinotive stands at the bottom with an average efficiency of 6 per cent. ; the compound non-condensing engine, 10 per cent. ; the compound condensing engine, including boiler, 13 per cent. ; the Parsons turbine, including the boiler, 17 per cent. Then follows the automobile motor with 23 per cent., the aeroplane motor with 27 per cent., the coal gas stationary engine with 30 per cent., and the average Diesel engine with 34 per cent. On reaching that modern development in which the internal combustion and tha steam engine are combined — namely, the Still type of engine, it was demonstratod to have an efficiency (actually obtained) of 41 per cent.; and the engineers who have been trying out these various types of power units set down the probable efficiency of the Still-Diesel eornbmation at 44.5 per cent. * In the Still-Diesel engine steam pressure is applied to force back tho piston after its being driven forward by the petrol engine internal combustion.