Engine Oil Pressure Low – Common Causes And Ways To Fix It

Engine Oil Pressure Low - Common Causes And Ways To Fix It
Engine Oil Pressure Low – Common Causes And Ways To Fix It

The first sign of trouble, may be a flickering oil light or a low engine oil pressure reading.

Consequently, low engine performance, engine noise and even poor starting, can all be caused by, low engine oil pressure.

Furthermore, if the warning goes unnoticed or is ignored, the next clue that something is wrong may be, valve clatter or ticking. Because, the hydraulic lifters or lash adjusters are starved for oil and ingest air.

Above all, when the engine oil pressure is too low, premature wear of internally lubricated parts, will result. So, any of these problems, should cause you to break out your mechanical oil pressure gauge.

Because, at this point you need to get a reliable reading. All engines will lose a certain amount of engine oil pressure over time, as normal wear, increases engine bearing clearances.

Mechanical Oil Pressure Gauge
Mechanical Oil Pressure Gauge

Unusually, low engine oil pressure in an engine, regardless of mileage, is often a sign that something, is seriously wrong. So, anytime a vehicle has a low oil pressure condition, don’t delay in investigating the cause.

But, problems with other systems and parts within the engine, can also cause a high or low reading.

Engine Oil Pressure Gauge Reading Low
Engine Oil Pressure Gauge Reading Low

Common Causes, Of Low Engine Oil Pressure Include:

Low Oil Level

  • The most obvious reason for the low oil pressure warning to come on is, the oil level actually being low. Consequently, the first course of action would be, to check the oil level on the dipstick. And, if the level is indeed low, you need to top up the oil. Next, you need to start your investigation of, where the oil is actually going.

Overheating Of Oil

  • The low oil indicator, also tends to light up when, the oil gets too hot and thins out.

Worn Engine Bearings

Engine Bearing Wear
Engine Bearing Wear
  • In a high mileage engine, low oil pressure is often due to, worn main and rod bearings. The oil pump itself, does not create pressure. It produces flow and the resistance to that flow, produces pressure. Therefore, as the bearings wear, clearances increase, allowing increased flow, which reduces pressure.

Worn Oil Pump

  • Another common cause of low engine oil pressure, is wear or excessive clearances, inside the oil pump. As a result, too much clearance inside the oil pump, will reduce the pump’s ability to pump oil efficiency. And, that reduces flow and pressure.

Oil Pump Pickup Screen Restrictions

Oil Pump Pickup Screen Restrictions
Oil Pump Pickup Screen Restrictions
  • So, restrictions in the pickup tube screen, can choke off the flow of oil into the pump. Again, reducing flow and pressure. Even a relatively small amount of varnish buildup on the screen, can restrict oil flow, at higher engine speeds. So, a coating only .005 inch thick, will reduce the total “open” area of each hole to .030 inches. Causing, a whopping 44 percent reduction in oil flow!

Weak Or Leaky Relief Valve

  • The pressure relief valve, can be located on the pump body or elsewhere on the engine. And, can be yet another cause of, low oil pressure. Most often, if the valve sticks open or is held open, by a small piece of debris. The valve opens, when pressure reaches a preset value (typically 40 to 60 psi).
  • This vents oil back into the crankcase and limits maximum oil pressure in the engine. The reason for doing so, is to prevent oil pressure from reaching, dangerous levels. High oil pressure, can be just as bad as too little. Consequently, excessive pressure, can rupture the oil filter or even blow out, pressed-in oil galley plugs in the block.

Faulty Oil Pressure Gauge

  • Sometimes, the oil pressure gauge itself, can be at fault. If you find that the gauge shows low pressure, after changing oil, there could be a problem with the gauge. Consequently, replacing the oil pressure gauge, should solve the problem.

Aerated Oil

  • Low engine oil pressure, may also be the result of, air in the oil pump. This normally happens when, the bottom of the crank churns up the oil in the sump. Aerated Oil, means that the oil has air bubbles in it. Usually, a sign that you have, too much oil in your engine. Also, bubbles in the oil, prevent it from lubricating the moving parts properly.

Dirty Oil And Engine

Oil Flow Restrictions
Oil Flow Restrictions
  • Sometimes, the engine may become starved for oil, at higher speeds. Because, the dirty oil is not returning quickly enough to the crankcase. Consequently, the underlying cause here, is usually severe varnish buildup, that restricts the oil return holes in the cylinder head.

Oil System Leaks

  • Leakage between the oil pickup tube and pump, and the pump and block, can suck air into the pump. Finally, it is not unusual to find engines, where the pickup tube has fallen off. And, that will cause a complete loss of oil pressure.

Plugged Oil Filter

  • A plugged oil filter can be yet another cause, of low oil pressure. All filters create a certain amount of resistance to flow, that increases, with the rate of flow. But, the amount is not much, typically only a couple of pounds. But, as the filter becomes clogged with debris, the restriction created increases.
  • Eventually, no oil will pass through the filter element. So, to prevent such a blockage, most filters have a pressure relief valve, located in the filter. This allows the oil to bypass the filter and keep on flowing. So, replacing the plugged filter, will solve the problem.
Low Engine Oil Pressure
Low Engine Oil Pressure

How To Test And Confirm, Actual Pressure Reading

Checking Oil Pressure with A Manual Gauge
Checking Oil Pressure with A Manual Gauge

So, engine oil pressure can be tested, by temporarily installing, a mechanical oil pressure gauge:


  • Bring the engine, up to operating temperature.
  • Now, shut the engine off.
  • Locate the oil pressure sending unit. Usually it is on the lower side of the engine block.
  • Disconnect the wire from the sending unit and remove the sender.
  • Install the oil pressure test gauge into the hole, where the sender was removed.
  • Check the engine’s oil level and fill, if required.


  • Now, start the engine and check the oil pressure on the gauge.
  • Watch as the engine warms, to note any excessive drops, due to temperature.
  • Record the measured oil pressure. Then turn off the engine.
  • Compare the test results, with the manufacturer’s specifications.
  • If the oil pressure is within specifications, this shows that the oil pressure sending unit, may not be working correctly.
  • In many cases, replacing the oil sending unit, will correct the problem.
  • After the test is complete, reinstall the oil pressure sending unit. Start the engine and confirm, there are no leaks.


Consequently, without engine oil pressure, an engine will experience, extreme internal engine damage, due to heat caused by friction.

So, no matter the mileage of you’re vehicle, it’s a good idea to pay attention to its engine oil. Because, it’s important to have the correct viscosity, at the correct level, adjusting for engine wear and seasonal changes. Finally, if the oil pressure warning light comes on, stop and check everything over. Before lack of lubrication, turns your engine into a paper weight.

Thank You !

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