When the engine oil needs to be changed at regular intervals, consult the owner’s manual to find out what the recommended interval is and how much oil is needed. The first step is to warm up the engine thoroughly. This will help to speed up the process by lowering the viscosity of the oil and allowing it to drain more quickly. Before removing the sump drain plug, locate a container large enough to hold all of the old oil, such as an oil can with the side cut out.

The oil filter is situated on one of the engine’s cylinder blocks. This one, a throwaway cartridge, is located near the back of the engine, beneath the rear spark plug. A cutaway view of a replaceable-element oil filter shows dirty oil passing through the external perforations and filter element before merging (clean) through the top central outlet.

There is no need to flush modern oils, which contain detergents, unless the old oil has been left in for an extended period of time. The final step is to clean any filters or separators on the engine breather. This is frequently found in the oil filler cap, which should be paraffin-washed, but it could be a separate unit located between the rocker cover (the casing on top of the main engine block) and the carburettor.