Check the level every morning with the dipstick, change the oil and filter at every service, and only use the grade listed in your owner's manual. If the level keeps dropping between services, get it checked.
How to read the dipstick
Use the right grade
Your owner's manual lists the oil grade for your engine. Petrol and diesel engines need different oils, so do not use whatever is left over from another vehicle. If you are not sure, your branch can tell you and sell you the right one.
What the oil is telling you
Black and thick
The oil is old and overdue for a change.
Milky or creamy
Water or coolant may be getting in. Stop and get it checked.
Level keeps dropping
A leak or the engine burning oil. Do not just keep topping up.
Gritty to the touch
Dirt is getting in, often through a worn air filter.
Changing the oil
Oil and filter are changed at each service. If you change it yourself between services, dispose of the old oil properly and keep a note of the date and odometer reading.