What are the seven causes of low oil pressure?

Low oil pressure in your car’s engine can be caused by an oil leak, a blocked oil filter, using the wrong viscosity oil, or a faulty oil pump.

Whatever the cause, you shouldn’t drive your car far if the low oil pressure light is on. Oil is essential for keeping the engine lubricated and a lack of oil will cause irreversible damage and can cause components like turbos to fail very quickly.

7 Causes of Low Engine Oil Pressure

Here are the top causes of low oil pressure in most engines.

1. Low Engine Oil Level

The first factor that could cause an improper pressure is low engine oil level. As simple as it is, many seasoned mechanics overlook oil level as the possible cause of a low-pressure problem. The engine oil level can go down due to many reasons:

• Oil leaks. This is one of the most frequent causes of low engine levels and should be addressed as soon as possible.
• Oil evaporation. Depending on the weather and oil viscosity you may experience oil evaporation. Even when it’s highly unlikely that this can affect the oil level in the short-term, can be one of many factors influencing the problem.
• Oil degradation. As will be explained in the next section, oil degrades over time. Degraded oil loses its properties (including viscosity) which has a direct impact on the lubrication system pressure.

2. Dirty or Degraded Engine Oil

Engine oil is subject to several conditions that degrade its properties over time. Some of these conditions are:

• The constant cycle of heating and cooling down.
• The friction forces of mechanical parts.
• The dirt, engine metal debris, and fuel contaminants that combine with oil.

The contamination/degradation process is inevitable due to the oil working environment. That’s why paying attention to the suggested oil change interval is important.

Typically, fully synthetic oil service intervals range between 7,500 to 10,000 miles depending on vehicle usage, brand, and engine design. The more you wait between changes the more likely your engine will suffer the consequences of degraded engine oil:

• Diminished cleaning power.
• Reduced wear protection.
• Higher viscosity

Arguably, the most dangerous consequence of all is the last one, higher viscosity which is discussed in detail in the next section.

3. Wrong Engine Oil Viscosity

Engine oil has many properties, but one of the most relevant is its viscosity.

Oil viscosity is so important that is used as one key parameter during engine design. Engine cavities and conduits are designed with a specific oil viscosity range in mind.

You may wonder how viscosity affects oil pressure and what it has to do with engine design.

Let’s assume that your engine owner’s manual recommends using 5W-20 synthetic oil. That’s a low viscosity oil, which means engineers most probably designed oil galleries with a tiny diameter. If you ignore the oil specifications and use a 15W-40 instead of 5W-20 then you will be using a thicker oil that presumably won’t flow through oil passages or if it does, will do it at a slower rate than the 5W-20.

When oil breaks down loses its lubricant properties, meaning that your engine parts will be exposed to metal-on-metal contact.

The result, a broken engine.

4. Clogged Engine Oil Filter

Engine oil filters are designed to capture contaminants, metal debris, dirt, and any other harmful element from flowing through the lubrication system.

Like any other filter, the engine oil filter is designed with a finite lifespan. Depending on the brand and engine oil type, you can expect a typical oil filter to last from 3,000 to 20,000 miles.

When the oil filter pressure reaches a certain value the relief valve opens and allows oil to flow through the engine, to help prevent damage. The oil is now bypassing the filtering element, which means it can quickly become highly contaminated and not work as it should.

5. Internal Engine Wear

Another factor affecting motor oil pressure is internal engine wear. As time passes, critical engine parts will wear down. The most frequent example on high-mileage engines is worn engine bearings.

Excessive wear on the crankshaft, crankshaft bearings, and rod bearings will decrease the overall oil pressure. That’s something to be expected because oil restriction when flowing through these orifices will be almost inexistent.

6. Faulty Engine Oil Pump

At the heart of the lubrication system is the oil pump. From a design standpoint, oil pumps should last the entire engine life of the engine. However, they can fail before that depending on vehicle maintenance and usage.

If the oil changes intervals were too prolonged, the oil level was kept too low for extended periods of time, or the vehicle was used in demanding assignments such as towing, police work, ambulance, and similar jobs, then the oil pump may fail prematurely.

7. Defective Engine Oil Pressure Sensor

Last but not least, the entire situation of low oil pressure could be a false positive.

Depending on the year and maker of your car this sensor could as simple as an electrical switch that sends to the Electronic Control Unit (ECU) a signal indicating low oil pressure or could be a more fully-featured pressure sensor.

If you have more questions about your vehicle and if there is an oil pressure issue – give us a call at The German Auto Doctor today.