4-Stroke Engine Oil, SAE 30, 1 Litre

Every four-stroke engine on a plot needs this: the lawn mower, the generator, the water pump, the tiller, the pressure washer. In a four-stroke the petrol goes in the tank and the oil goes in the sump as two separate things, and the oil in the sump is the only thing standing between the moving parts and each other.

SAE 30 is the straight grade most small air-cooled four-stroke engines are specified on, and it is what a mower or a generator manual usually asks for in a warm climate. A one litre bottle is the practical size. Most small engine sumps hold well under a litre, so one bottle covers an oil change with a little left for topping up. The reason to change oil rather than only top it up is that a small air-cooled engine runs hot and the oil darkens and thins with use, and old thin oil protects nothing.