Chances are, if you accidentally cut a finger wide open while slicing and dicing veggies for your stir fry, you simply continue on as if nothing happened. After all, what’s a little blood loss, right? No! That’s not right! Not only does it cause a mess and spoil your food, but you are losing blood. Blood your body needs. So, you clean the cut and stop the bleeding as soon as possible. You wrap up the wound and head to urgent care so a doctor can close it up with a stitch or two or three.
Well, motor oil is often considered the “lifeblood” of your engine. It is essential. And it needs to remain inside your engine to be of any value. But sometimes it leaks out. Why? There are a number of causes of an oil leak. And there are a number of ways to spot one.
What oil does for your engine
Yes, motor oil (also called engine oil) is pretty important. Without it, your engine would fail in short order. How does oil affect your engine? The primary purpose of motor oil is to lubricate all of the moving metal parts inside an engine. It creates a thin coating on the pistons, cylinder walls, valves, and other parts to keep them from touching one another. You do not want your valves to make metal-to-metal contact with their guides, or your camshaft to rub directly against its bearings. All of those internal components need to be separated from one another by a wafer-thin layer of oil that reduces friction between them.
Motor oil also helps to control heat. As a lubricant, oil allows the parts of your engine to slide easily, even though they are extremely close to one another. And when the oil comes in contact with those metal parts, it absorbs some of the heat.
Above all that, motor oil contains special additives that serve to reduce friction, improve viscosity, and clean your engine.
When your car is not running, the oil sits in a sump on the bottom of your engine, the oil pan. Once you start it up, an oil pump functions like your heart and circulates oil throughout the engine. The oil travels through small passages (galleries) similar to your arteries and veins. The oil is constantly forced through your engine and eventually makes its way back to the oil pan, where it can cool off. Along the way, an oil filter removes particulates or other impurities, just as your kidneys clean your blood.
Traditionally, motor oil has been derived and distilled from crude oil pumped from the ground. This “conventional” oil, while still very common, is gradually being replaced by vehicle manufacturers with synthetic oil created artificially in a lab (such as industry-leading Mobil 1™ synthetic motor oil). Because it is carefully engineered from high-quality base stock, synthetic motor oil boasts a number of advantages.
Whatever type of oil it uses, it is imperative that your engine operates with the proper amount of clean motor oil.
Signs of an oil leak
The first and most obvious signal that your engine has sprung a leak is a brown puddle underneath the front of your car, truck, or SUV. Fresh motor oil is an almost-transparent honey color, but it turns dark brown to near black as it ages. This color change is normal; dark oil is not itself a sign that your oil is dirty. If you see an oil spot, you likely have a leak.
But modern vehicles have shields underneath the engine that can prevent a slight leak from reaching the ground. Instead, the oil might pool on top of a shield. So, it is important to check your oil regularly, a couple of times each month. Open the hood, locate and remove the oil dipstick, and make sure the oil level reads somewhere between the high and low marks. Again, you are not trying to discern if the oil is good or bad – that can only be decided by a chemical analysis – you are simply gauging the level. If the level is low, you can add a bit of the right type and grade of oil to top it off. Most engines will burn a small amount of oil, but excessive oil consumption is not normal. If you find that your car eats oil regularly, you likely have a leak or some other engine problem.
You can also inspect the outside of your engine for signs of an oil leak. Look for seepage or dirty buildup. Oil can mix with dust and dirt and get caked in the crevices on a motor. Oil seeping from your engine, especially if it builds up considerably or leaks onto hot exhaust components, can become a fire hazard.
And if the oil does hit a hot exhaust pipe, manifold, or other heat sources, it can burn. And smell. Another sign of an oil leak is a burning smell when your engine is running. You might notice the odor when you are driving, when you pull up to a light with your windows down, or even when you put your car in park and step outside. Burning smells are not a normal part of the driving experience. They mean something is likely wrong. And that “wrong” could be an oil leak.
Reasons for an oil leak
Sometimes an oil leak is due to poor maintenance procedures: a loose oil filter or oil pan plug, or an oil cap that someone forgot to replace. Those can be the result of seeking out a cheap service that ends up costing more in the long run. More often though, an oil leak happens when an engine’s seals or gaskets deteriorate with age or lack of maintenance. Sometimes a defect from the manufacturer leads to a shorter-than-normal lifespan for a gasket. Other times, it is because the oil was not replaced regularly.
Your engine has many seams and connections, each of which must be sealed tight to prevent fluid leaks. The oil pan, valve covers, intake manifold, heads, timing cover, oil cooler lines (on some engines), camshaft seals, and rear main seals for the crankshaft (on all engines). Each of these presents an opportunity for an oil leak.
Every so often, your oil needs a transfusion. Over time, motor oil deteriorates. It breaks down, producing sludge and corrosive compounds. Sludge can build up inside your engine and cause all sorts of problems. Those corrosive materials can eat through engine seals and create leaks. These conditions can happen – will happen – if you neglect to have your oil changed when it should be changed. Questions about when you should replace your oil? Forget the old outdated standard of three months or three thousand miles. Instead, learn what your vehicle manufacturer recommends for the time between oil changes.
What to do about an oil leak
Some folks might suggest that you simply put thicker oil in your car to treat a leak. Sounds reasonable. It is not. Sure, in theory, thicker oil would have a harder time fitting through gaps in your engine. Honey has a tougher time seeping through a crack than water does. But thicker oil, oil with a higher viscosity, also has a hard time fitting between the tight tolerances of a modern engine. That means not all of your engine parts are lubricated because thick oil cannot fit into tight spaces. Stick with the oil recommended (required) by the manufacturer.
And ignoring an oil leak does not make sense any more than ignoring a bleeding finger. Your engine does not have a clotting feature; it does not heal itself. A small leak can turn into a larger one. Plus, that oil on the ground is a slip hazard and a pollutant.
If you notice any of the signs of an oil leak, check the level. If it is low, top it off. And then, make an appointment with a technician at a trusted repair shop who can diagnose the source of the leak and repair it right.
Of course, an oil leak is not the only fluid leak that can happen to your car. Leaks can come from your transmission, brakes, cooling system, power steering, air conditioning, and more. Fortunately, many shops offer a complimentary courtesy check (that includes looking for leaks) when you take your car in for an oil change or other routine maintenance.
