There's a mystery afoot! If your low oil level light keeps flashing on, it can sometimes feel like a bandit is coming in the night to steal your car's precious fluids. While severe oil leaks often leave significant evidence on garage floors and other surfaces, some oil can disappear without a trace. Investigating these disappearances can sometimes make you feel like you've stepped into an X-Files episode.
Fortunately, there's almost always a rational explanation for oil that vanishes into thin air. Here are three causes for your missing oil that are more likely than oil thieves or little green men.
1. Valve Cover Gasket Leaks
A puddle of oil under your car is never a good sign, and it's often a good indication that you should think twice before turning the key. Most oil leaks aren't nearly this dramatic, however. Smaller leaks often occur at gaskets, where two parts must join together. As the name implies, the valve cover sits on top of your engine's head. The gasket ensures that oil doesn't escape while the engine is running.
Repeated heating and cooling cycles can turn this rubber gasket into plastic, resulting in tiny leaks. The position of the gasket means that oil rarely falls onto the ground, but instead drips onto hot exhaust components. When this happens, the oil burns away. Severe valve cover gaskets leaks sometimes produce a noticeable odor of burning oil, but frequently the oil can seem to simply disappear.
2. Blowby Losses
During the process of combustion, some of your engine's air/fuel mixture can escape beyond the combustion chamber. These gases are known as blowby, and modern vehicles use positive crankcase ventilation (PCV) systems to catch and recycle this waste. Most cars use a straightforward valve to ensure that blowby gases cannot directly return to the combustion chamber.
PCV failures can lead to several situations that may result in burnt oil. Depending on the underlying type of failure, oil may mix with the blowby gases, or crankcase pressurization may be pushing oil into the cylinders. In either case, this problem can eventually damage internal engine seals, so you should never ignore it.
3. Failed Seals, Piston Rings, or Other Internal Issues
In some cases, a breakdown of internal engine seals may be at the core of any missing oil mystery. Since your engine relies on oil for lubrication, various internal seals help to prevent fluid losses. As these seals wear away, oil can make its way into the combustion chamber and burn up. An engine that's burning oil in this way may also experience power losses, fuel inefficiencies, or other driveability problems.
Your engine should not lose oil when operating normally. If you've got a missing oil case on your hands, always have your car evaluated by a professional technician at an auto repair shop to determine the true culprit.