Most car makers recommend that engine oil is changed and the oil filter renewed at 5,000-6,000-mile intervals, or every six months. The figures for your car can be checked in the handbook.

Oil is drained after removing a plug at the base of the sump. Before beginning, look underneath at the drain plug—if it has a hexagonal or square recess or a squared end, a special tool may be needed to loosen it.

Oil flows more readily when hot and is best drained after the engine has been warmed up. The sump is designed to drain when the car is on level ground.

If necessary, raising one side of the car a few inches with the jack will provide enough room to reach under- neath and loosen the plug, but do not get under the car unless the vehicle is properly supported. Lower the jack once the plug is loose.

Use a shallow container to catch the oil. If the sump holds more than five litres (check in the handbook) an old washing- up bowl will do. Better is an empty 5-litre oil tin laid on its side with a large square hole cut in the upper side. The tin- plate is thin enough to cut with an old pair of stout scissors, but be sure to turn over the edges of the metal with pliers —this prevents cut fingers when the tin is moved. Pur- pose-made plastic drain cans are also available.

It is illegal to pour old engine oil down the drain; it should be poured into a container (the filler neck on the cut-out oil tin helps here) and taken to the nearest local authority rubbish area. A discarded filter can be wrapped in a plastic bag and put in the dustbin.

Current practice is to one-piece throw-away’ cartridge-type filter which screws directly onto the crankcase or on to a filter housing. Earlier engines use bowl- type filters which must be dismantled to remove the filter element inside, cleaned, and a new element inserted. Not all engines have external

fit a filters. Volkswagen air-cooled engines have an internal strainer (see Project 19), while as well as an external filter, some engines also have a centrifugal filter, which is usually incorporated in the crankshaft pulley. These are generally serviced only at long intervals—around 24,000 miles.