4-Stroke Engine Oil, SAE 30, 5 Litres

This is the size to buy when you are looking after more than one machine or servicing them regularly. A farm with a generator, a water pump and a mower gets through oil steadily, and buying five litres at a time costs less per change and means you never put off a service because the bottle is empty.

SAE 30 is the straight grade most small air-cooled four-stroke engines specify, and it is the common recommendation for mowers, generators and pumps working in a warm climate. Five litres covers several oil changes on typical small engines, since most of these sumps hold well under a litre. The reason to change oil on schedule rather than just topping it up is that small air-cooled engines run hot, and the oil darkens, thins and loses its film strength long before the level drops. Old oil in a full sump protects far less than it looks like it should.