Contrary to popular belief, cars do not use up engine oil. If your car is consistently low on oil, you either have an oil leak or an engine that’s burning oil. You can detect the latter condition by blue smoke coming out of the tailpipe. Cars that burn a lot of oil are candidates for engine rebuilding. Although you may not be able to fix an oil leak, you can help diagnose it, saving your mechanic’s time (and your money).
1. Open the hood and look for obvious signs of wetness. Oil leaks usually come from a gasket: a piece of material, usually rubber, cork or silicone, that creates a seal between two metal parts. Look for places where different parts of the engine are bolted together.
2. Inspect underneath the car with a flashlight for signs of wetness. Oil here could be from a leak under the engine, or it could be collecting from a leak higher up. Wipe the suspect areas clean with a rag so you can inspect them closely and pinpoint the leak’s source.
3. Consider getting the engine professionally steam-cleaned at an auto-repair shop if oil has leaked everywhere. This will make it easier for you or your mechanic to locate the leak.
4. Place a large piece of cardboard on the ground under the engine. Make marks on the cardboard to indicate its location in relation to the tires and the car’s front and rear. Leave it in place overnight. Use rocks to hold it down if you park outside. (Some oil leaks occur only when the engine is running, but the cardboard method described here will still help locate these kind of leaks, because the oil will drip down.)
5. Check the cardboard in the morning to determine the amount of leakage and where it’s dripping from.
6. You may find other types of leaks. Motor oil out of the bottle is the color of honey. Oil that has been in the engine for a little while is dark brown or even black. Coolant is green and smells sweet. Brake fluid is very light brown (almost clear) and very slippery. Automatic-transmission fluid and power-steering fluid are usually red.
Repair leaks as they occur. It is more difficult to diagnose a leak when everything is wet and seeping than on an otherwise dry and clean engine.
If you have a leak, be extra vigilant about checking all fluids regularly.
Stop driving immediately if the oil light on the dashboard comes on. Running an engine without enough oil will lead to very expensive repairs.