Penrite Classic Heavy engine oil 40W/70 can be used to replace SAE 50 oils, with noticeably better results than using a 20W50 in some applications.
Classic Heavy is a multigrade oil made especially for engines that were manufactured between 1950 and 1975, such as those that called for SAE 50 monograde, or where castor oil was originally recommended. Ideal for both cars and many British motorcycles using ball and roller bearings.
This broad spectrum multigrade Penrite oil means that starter motor cranking loads are reduced in comparison to a mongrade oil, whilst hot oil pressure is improved. Classic Heavy was previously sold in the UK under the name HPR50.