Reasons why Engine May be Low on Oil - Subaru Service Questions in Olympia, WA
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Why is your Subaru's engine oil low

The lubrication system in a modern engine is totally closed. That means however much liquid is in the system, that's how much should always be in the system. It should never lose much if any oil.

Having said that, it's still a good idea to periodically check your engine oil level. If it's low, you have a problem with the engine either leaking oil somewhere slowly over time, or the engine is burning the oil during combustion.

While you can safely operate a car with an engine that's burning a little oil, or one that's got a minor engine leak, you have to keep a close eye on the oil level and top off the system as necessary. Running the car with insufficient oil can lead to friction damage from metal-on-metal contact and overheating -- both of which can utterly destroy your engine over time!

We'll explain on this page the five most common ways an engine loses oil, and how to address them.

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Reason #5: Oil Pan Leak

Underneath the engine sits the oil pan, where the oil settles as the engine cools once the car has stopped running. Because it's located on the bottom of the car's undercarriage, the oil pan is susceptible to damage from things like debris in the road, going over speed bumps too fast and striking obstacles off-road. If the oil pan gasket (AKA the sump gasket) gets ruptured, or a crack develops in the oil pan itself, oil will surely begin to leak out. You're likely to notice a black or brown splotch on the ground beneath your car. Thankfully, replacing the oil pan and gasket is one of the easier ways to address an engine that's losing oil rapidly.

Get answers about engine oil and why it could be low

Reason #4: Random Oil Leaks

Just about anywhere on the engine is liable to spring a leak of some kind. Since oil is circulated throughout the entire engine, there are all sorts of places where a small gap or crack could allow oil to seep out: things like rear main seals, head gaskets and other points on the engine could leak. Unlike the oil pan, these parts can't usually be damaged by features of the road. They simply wear out and begin to leak over time. It's just ordinary wear-and-tear.

While you might be able to spot an oil puddle if the leak is fast enough, or you might be able to see signs of oil drips if you look under the car, a slow oil leak near the top of the engine might not leave any visible signs of a leak on the ground. That's why you've got to check the oil level periodically. If the oil level continues to fall, turn to a professional to stop the leak.

Reason #3: Bad PCV Valve

The first two reasons a car engine might lose oil is due to a leak. The last three have to do with an engine burning oil, which can be a much more significant problem.

However, a bad PCV valve is a tiny, inexpensive part that can cause an engine to burn oil if it goes bad. Replacing it is fast and easy! If your engine is burning oil, hope that it's due to a bad PCV valve.

The PCV valve is designed to allow air to escape the crankcase when the pressure inside grows too high -- but when it malfunctions, it can begin sucking oil into the engine and burning it there instead. A replacement PCV valve will have to be installed. The engine will simply burn the oil left inside it, and the new PCV valve should keep things working as they should without burning any additional oil.

Reason #2: Bad Valves and Valve Guides

The last two reasons that an engine burns oil can be costly to fix and require the expertise of a factory-trained technician. The first are bad intake and exhaust valves in the cylinders.

These valves open to allow air and fuel into the combustion chambers, and allow exhaust gasses to escape. They open and close extremely rapidly, and engine oil lubricates them so they can open and close dozens and even hundreds of times each second. Over time, wear on the engine can allow the valves themselves to begin to leak oil into the cylinders -- where the engine will promptly burn the oil. You'll need to have new valves and valve seals installed in your engine to stop the oil burning. Or, if a mechanic recommends it, you can simply allow the engine to burn a little oil. Just keep the oil level where it needs to be by checking the level regularly and adding a little oil as necessary.

Reason #1: Bad Piston Rings

This is extremely similar to the problem described in reason #2, but from the other side. The valves are located at the top of the combustion cylinders; located on the bottom is the piston. The piston travels up and down the cylinder, and piston rings seal it against the cylinder walls so no oil can seep past. Over time, these piston rings can wear down. As they wear, they'll allow oil from the crankcase to seep past the pistons, where the oil will be burned by the engine. New piston rings can be costly, but it'll be a necessary procedure to keep the engine from burning oil. Or, if your car's already got significant mileage on the clock, you can just allow the engine to burn some oil and continue taking care of it until it finally gives out. Burning significant amounts of oil internally is often an indicator that your engine has simply begun to wear out due to age.

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Hanson Subaru

2300 Carriage Loop SW
Directions Olympia, WA 98502

  • Call or Text Sales: 360-943-2120
  • Service: 360-943-2121
  • Parts: 360-943-8531
  1. Hanson Subaru

    2300 Carriage Loop SW
    Olympia, WA 98502

    • Sales : (888) 490-9863

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