Car Engine Burning Oil

Oil plays a critical role in reducing the friction inside an engine while also helping to maintain a safe operating temperature for internal combustion. As time passes, it’s natural for your car to burn a miniscule amount of oil, though not anything that you should notice within the span of a standard oil change.

Suppose a mechanical fault like compromised valve seals or worn-out piston rings allows excess oil into the combustion chamber. In that case, you might notice blue smoke coming out of the tailpipe, the engine running abnormally hot, or the oil pressure gauge on the dash cluster running lower than usual. These are all early signs that your engine is burning more oil than it should. You need to find out what’s causing it and get it fixed, or you risk even more expensive engine damage.

Yet, there are a lot of different mechanical faults that could cause your engine to burn oil. Each has its own secondary symptoms. Understanding them can help you dial in on what needs to be fixed and how to prevent future burning oil problems.

5 Common Symptoms of an Engine Burning Oil

Blue smoke from the tailpipe is one of the most common signs that your engine is burning more oil than it should. This usually comes along with foul burning odors in the engine bay and exhaust system. If you ignore these signs, they will likely worsen, and you will notice other problems developing, such as the engine running hot or the low oil warning light coming on.

1. Blue Exhaust Coming Out of the Tail Pipe

blue Exhaust Coming Out of the Tail Pipe

Blue smoke coming out of the tailpipe is one of the most common signs that your engine has started burning oil. The exhaust manifold might even belch big plumes of blue smoke when you start the car or step down hard on the gas pedal to accelerate quickly.

The most common mechanical faults causing burning oil and blue smoke include excess wear and tear on engine components such as piston rings, valve seals, or Positive Crankcase Ventilation (PCV) valves.

2. Strange Burning Oil Smells

Strange Burning Oil Smells

Strange burning smells with a hint of petroleum vapor to them can also indicate that your engine is starting to burn more oil than it should. However, it can be hard to tell if this is from an oil leak causing oil to drip down onto hot engine components or if it’s oil burning in the combustion chamber or other internal engine components.

To ferret out, which is the case, you should look for obvious signs of an oil leak, such as drips under the car after it’s sat parked after driving or signs of black sludgy carbon deposits on the outside of the exhaust manifold. Also, check for signs of an oil leak around the valve cover, drain plugs, front main oil seal, rear main oil seal, the oil pan gasket, and the oil filter housing,

Suppose you can’t find any overt signs of an oil leak allowing oil to drip into the engine bay. In that case, your next assumption has to be that some internal mechanical fault allows excessive oil to burn in the cylinders.

3. The Engine Starts Running Hot

The Engine Starts Running Hot

As your car burns oil, the decreased volume allows more friction between the pistons and the cylinder walls. As the heat energy builds, the cooling system struggles to keep up. The coolant circulating gets hotter and hotter. The engine coolant temperature sensor on the radiator sends this data to the ECU, and the dash display shows the engine is running hotter than usual.

This is a fault that can slowly manifest. The weather is particularly cold, especially if you’re just driving on the highway or the outside. Then, when you get stuck in stop-and-go traffic or it’s a hot day, the engine temperature starts to creep up to the point that the engine is at serious risk of overheating.

It’s easy to misinterpret a hot running engine as a problem with the cooling system rather than when it’s actually due to burning oil. If you check the engine coolant levels and they look normal, the fluid is clear, and the radiator fan is running like normal, you should check the oil. If it’s low on the dipstick, you’re either burning oil or having an unknown oil leak, even when the engine is cold.

4. Fouled Spark Plugs

Fouled Spark Plugs

The more oil your engine burns and the hotter it runs, the more likely you are to experience spark plug problems. This can further add rough idle and occasional misfires to the slew of confusing symptoms you’re dealing with. More than one DIY mechanic can have confused these signs for an ignition coil failure, only to blow an hour or two, testing all the coils to find out they’re all perfectly fine!

If you pull one or two spark plugs that are badly fouled or blistered, and the ignition coil associated with it tests normal on a multi-meter, then it tells you that your oil-burning problem lies elsewhere. The spark plugs are simply a secondary symptom but one that will also need to be dealt with in the grand scheme of things.

5. The Oil Warning Light or Check Engine Light Comes On

The Oil Warning Light or Check Engine Light Comes On

As you continue to burn oil, the oil pan level will eventually reach the point where the oil warning light or the check engine light comes on. At this point, the wisest move is to pull over and park the car. You can then get it towed home or to the local mechanic. If you’re a DIYer, the check engine light will also throw a code to help you dial in what’s wrong.

  • Code P0420 is a code for a catalytic converter problem that might initially seem odd. However, it’s usually because there is so much oil residue and carbon in the exhaust system and catalytic converter that it starts to clog, affecting the overall performance of the exhaust system. This double-whammy sign tells you the oil-burning problem has been left unchecked for far too long!
  • Code P0401 is a generic code noting that the ECM has detected the EGR valve isn’t flowing enough recirculated exhaust gases into the intake manifold. This is often due to carbon deposits and oil residue fouling the valve.
  • Code P0524 and P0522 are triggered when the oil sensor detects that the amount of engine oil pressure is too low. In this case, the engine has been burning oil to the point where it’s critically affecting the oil level.

5 Causes an Engine to Burn Oil?

While the engine naturally burns a tiny bit of oil over time, a significant oil-burning issue is often due to a mechanical fault in the PCV valve, damaged seals, or worn piston rings. Other things like a blown head gasket or oil seeping into the turbocharger are also in play.

1. Damaged Valve Seal & Guides

Damaged Valve Seal

When valve seals or guides are compromised, oil is allowed to leak into the cylinders during the internal combustion process, burning it along with the gasoline. This problem tends to start out small and might be mistaken for part of the natural process of oil being burned through normal engine combustion.

Yet as the valve seals further degrade, more and more oil enters the combustion chamber, causing increasingly dense bluish smoke as it burns. This type of leak can get worse quickly if the valve guides are worn out.

How to Diagnose Damaged Valve Seals & Guides

Blue smoke from oil being burned in the combustion chamber, misfires, poor acceleration, and a very rough idle are common signs of damaged valve seals and worn-out guides. To confirm damaged valves, you’ll need to perform a compression test.

How to Fix Damaged Valves & Guides

Replacing damaged valve seals can be a labor-intensive job that is usually beyond what the average DIY mechanic can handle independently. The part cost itself isn’t the problem, as a new seal will only set you back around $25 to $50. However, some foreign models might cost you as much as $150.

The problem is that a mechanic’s labor time is going to add another $140 to $350 to the job. Perhaps more if worn-out guides are also at play.

2. Worn Out Piston Rings

Worn Out Piston Rings

Worn-out piston rings can let an increasing amount of oil into the cylinders where it’s burned, creating blue smoke. As the problem worsens, the burning oil leaves behind excessive carbon deposits on the cylinders and piston rings. In time, they can even start to migrate into the exhaust system, gradually clogging the catalytic converter.

Most cars have three different types of rings, which can allow oil into the combustion chamber as they fail.

  • The Compression Ring – helps the piston to compress the fuel/air mixture without leaking to maintain the ideal level of compression for the internal combustion process.
  • The Wiper Ring – Serves as a backup piston ring that prevents any gas leakage beyond the compression ring when the fuel/air mixture ignites. It also“Wipes” away any excess oil from the cylinder wall. If the wiper ring fails, a small amount of oil is left behind, which is picked up and burned in the next piston cycle.
  • The Oil Control Ring– is designed to return any excessive oil drawn away from the cylinder wall to the oil pan by the wiper ring. If it also fails with the wiper ring, the amount of oil lingering in the combustion chamber can be high. Sometimes, it is high enough to affect engine performance and possibly cause misfires.

When rings start to fail, the blow-by gases entering the crankcase also include excess oil vapor, which is then pushed back into the intake tract via the PCV system. Thus creating a vicious cycle of engine faults that will only get worse. Sometimes, in a short amount of time.

How to Diagnose Worn-Out Piston Rings

Along with blue smoke from burning oil, worn-out piston rings will also cause the engine to feel down on power, along with other signs of a compression problem. The engine will also have a hard start and idle rough.

The large amounts of oil that get burned due to worn-out piston rings will also cause the oil level on the dipstick to drop quickly. If you pull a spark plug or two, you’ll likely notice oil residue or carbon buildup on the plug.

How to Fix Worn-Out Piston Rings

Replacing bad piston rings is a labor-intensive nightmare, as you have to take a lot of engine components apart just to get to them. This requires a bevy of special tools and skills that are typically beyond what a capable DIY mechanic can handle.

Even if you think you can handle the piston ring replacement, many other things could go wrong along the way. So, the wisest move is usually to have a mechanic handle it.

The part cost for the new piston rings is relatively low, averaging between $35 to $125.

The mechanic’s labor cost to tear so much of the engine apart to replace the rings and reassemble everything will easily add another $1,000 to as much as $2,000 to the final bill. With some models, the labor cost can exceed $3,000, which might make ring replacement a questionable call for an older car.

3. A Blocked or Worn PCV Valve

Blocked or Worn PCV Valve

Excess oil in the crankcase can start burning anytime the Positive Crankcase Ventilation (PCV) valve is blocked or partially obstructed. In a normally functioning engine, the pistons produce combustion gases that generate a regulated amount of pressure in the crankcase. These combustion gases are supposed to be recirculated back to the combustion chamber via the PCV valve, where they are burned before being sent out through the exhaust system.

If the PCV valve is worn out, blocked, or even partially clogged, it can lead to oil blowback, where lingering oil is burned instead of gasoline. This will cause blue smoke to come out of the tailpipe while also affecting engine performance with stalls, an overly rough idle, and even occasional misfires. If the engine burns oil for too long due to a clogged PCV valve, oil and carbon deposits can also be left in the catalytic converter.

How to Diagnose a Bad PCV Valve

If your car has a PCV valve (Not all do), you should be able to find it on the valve cover, the intake manifold, or the side of the block. You can then test it using the following steps.

  • Step One: Start the car and let the engine reach operating temperature.
  • Step Two: Carefully remove the PCV hose and place your finger over the end to block it completely.

You should feel a small amount of vacuum suction, and the engine RPMs should drop for a moment before stabilizing. If you don’t feel any suction or the engine doesn’t respond, the PCV valve is likely clogged.

  • Step Three: Look at the end of the hose for carbon deposits.
  • Step Four: If the Check Engine Light has recently come on, you can check for codes P0171 and P0174, indicating a PCV valve performance problem.

How to Fix a Clogged PCV Valve

If your car is burning oil due to a clogged or worn-out PCV valve, you can try to clean it yourself by soaking it in a carburetor cleaner. However, this is more of a quick fix. Most automakers consider PCV valves to be maintenance items that need to be replaced every 30,000 to 50,000 miles or so.

The part cost for a new PCV valve generally costs less than $20, and replacing it is something even a modestly capable DIY mechanic can handle on their own with the following steps.

  • Step One: Locate the PCV valve and carefully disconnect the hose and any sensor leads there might be.
  • Step Two: Turn the valve counterclockwise to disengage it from the tubular housing.
  • Step Three: Visually compare to make sure the new PCV valve is an exact match for the old one.
  • Step Four: Insert the new PCV valve and turn it clockwise to lock it in place. Make sure the locking tab engages.
  • Step Five: Reconnect the hose and any sensor leads.
  • Step Six: Clear any codes and take the car for a 20 to 40-minute test drive to clear any lingering oil residue from the crankcase.
  • Step Seven: Park the car with the engine running and have an assistant rev the engine while you watch the tailpipe.

If the PCV valve was the only fault causing the engine to burn oil, it should be cleared up or perhaps you’ll see the slightest tinge of blue smoke from residual oil in the system. If you are still burning oil with copious amounts of blue smoke or the engine is still running rough after the test drive, then there are likely additional problems that need to be found.

Note

When a PCV valve gets clogged, or the engine has been burning oil for a long time, the residual oil can easily foul the spark plugs. So, if you replace the PCV valve and you have no blue smoke, yet the engine is still running rough, check the spark plugs to see if carbon deposits foul them. If they are, the spark plugs will also need to be replaced.

4. A Blown Head Gasket

Blown Head Gasket

Even the slightest failure in the head gasket that marries the cylinder head to the engine block can allow an engine to burn more oil than it should. Compounding this problem is that it can also allow coolant to mix with the oil as both fluids infiltrate the combustion chamber. This can cause white, sweet-smelling smoke from the burning coolant to come out of the tailpipe, along with blue-tinged smoke from the burning oil.

How to Diagnose a Blown Head Gasket

Since a blown head gasket also interferes with the engine cooling system, you’ll likely notice the engine running increasingly hot, especially in stop-and-go traffic. A blown head gasket can also cause coolant and oil to mix. The oil on the dipstick will tend to look bubbly or a little bit like chocolate milk, and the coolant in the reservoir will probably look a little sludgy.

How to Fix a Blown Head Gasket

https://youtu.be/fhU_56cruIA

If the leak in the head gasket is minor and you only see small signs that the engine is burning oil, you might be able to batch it with a sealant additive like Blue Devil temporarily. This calls for draining the radiator and refilling it with water before pouring in the specified amount of sealant.

You then take the car for a half-hour or so drive to warm it up and let the sealant circulate through the system. Then drain the radiator again and refill it with antifreeze and water like normal. This will patch a minor leak in a head gasket for three to six months, which should buy you the time you need to save up for the proper head gasket replacement.

If the sealant doesn’t work or you see severe signs that the head gasket is severely blown, it must be replaced. Procrastinating a repair like this will just cause the engine to burn even more oil and coolant while also risking a crack in the cylinder head itself.

This isn’t the sort of thing that the average DIY mechanic can do. The wise move is to have it professionally repaired, especially since your coolant system and radiator fluid are likely fouled as well.

The part cost for a new head gasket is usually less than $100.

However, the labor cost to have a mechanic replace the blown head gasket can be as much as $1,500 to $2,500.

5. Turbo Charger Seal Is Leaking Oil

Turbo Charger Seal Is Leaking Oil

If your car has a turbocharger and the seal is compromised, it can let a miniscule amount of oil into the system, which will inevitably get burned with the turbocharger gasses. Oil getting into the turbocharger will also foul up the bearing, which will cause a high-pitched whistling or whining sound.

Diagnosing an Oil Leak in a Turbo Charger

If your car is burning oil, making a high-pitched whine, and feeling down on power when you accelerate hard, chances are good that the seal in your turbocharger has failed. You’ll likely also notice blue or black smoke from the tailpipe.

A lot of times, oil leaking into the turbocharger will eventually cause the check engine light to come on and throw a code.

Code P2262 is the diagnostic trouble code for Turbo Boost Pressure Not Detected-Mechanical.

How to Fix a Turbo Charger with an Oil Leak

If the oil seal is minor, you might be able to get away with a minor partial turbocharger rebuild. Though the oil almost always kills the bearing. So, to have a mechanic rebuild/fix the turbo will set you back around $300 to $450.

Most of the time, the turbocharger needs to be replaced as the damage is too extensive. The part cost for the replacement turbo can vary wildly, though the average tends to be around $450 to $700. Then, a mechanic will add another $350 to $400 in labor costs for a final repair bill of $750 to $1,100.

Common Problems Caused by An Engine Burning Oil

Continuing to drive a car that’s only burning a little oil is as tempting as it is dangerous, as you risk damaging or fouling many different things.

1. Fouled Spark Plugs

Fouled Spark Plugs

Most engines that burn oil also end up fouling the spark plugs with carbon deposits. This can lead to engine performance issues and even dangerous misfires. Even after you fix the underlying cause of the burning oil, you’ll likely also need to replace the spark plugs.

2. Clogged Catalytic Converter & Exhaust Manifold

Clogged Catalytic Converter & Exhaust Manifold

The longer you allow your engine to burn oil, the more carbon deposits and debris you’ll get in the exhaust manifold and the catalytic converter. If you catch it early enough, you might be able to pour some catalytic converter cleaner into the fuel tank to clear the deposits without needing a mechanic’s intervention.

3. Cooling System Damage

An engine that burns out and runs low on oil will inevitably suffer more heat from friction. Especially if you do a lot of stop-and-go driving. This can cause the engine to run excessively hot and even strain the cooling system. Boilover events and degraded coolant are often side effects of burning oil. So, if you check your coolant and it looks discolored or sludgy, the wise move is to perform a complete radiator flush and fill.

4. A Blown Head Gasket or Cracked Cylinder Head

Blown Head Gasket or Cracked Cylinder Head

The excessive heat from friction caused by burning oil and low oil can get so severe that it causes the head gasket to fail or potentially even crack the cylinder head. Even if the original problem had nothing to do with the head gasket at all!

If your car started burning oil due to something simple like a clogged PCV valve, and it starts blowing white smoke afterward with a tinge of blue, you might have blown the head gasket or cracked the cylinder head.

Frequently Asked Questions

How Much Oil Does an Engine Normally Burn?

It’s normal for a gasoline engine to burn a tiny amount of oil in between oil changes. Some automakers expect a typical engine to burn around a quart of oil every 1,500 to 2,000 miles. Some high-performance engines might even burn through a quart of oil in a thousand miles. This is one of the many reasons why it’s important to check your oil at least once a month periodically.

Will a Car Burning Oil Pass an Emissions Test?

Emissions tests accept that the average engine will burn a little oil, and there’s an allowable threshold. Though even the slightest tinge of blue smoke coming out of the tailpipe will likely cause your car to fail a standard emissions test.

Conclusion

An engine burning oil will usually show up as blue smoke coming out of the exhaust, and the engine will likely start to run hot from excess friction between the piston/rings and the cylinder walls. Several mechanical faults can cause this. If you’re lucky, it’s just a clogged PCV valve, which you can replace for less than $100. Most of the other causes are likely more severe and will cause additional symptoms to help guide your troubleshooting efforts.

Bad rings that allow excess oil to enter the combustion chamber are a common cause of burning oil and an expensive one to fix. The parts cost isn’t the problem, but the labor involved in tearing down the engine just to get at the bad rings can be prohibitive.

A blown head gasket is another common cause of burning oil. It usually also allows the engine coolant to mix with the oil, producing white smoke with a blue tinge in the exhaust. You’ll likely also have overheating problems to deal with. You might be able to patch the damaged seal with a sealant additive temporarily. However, it will just take you three to six months to get the head gasket completely replaced.

If your car has a turbocharger and it’s recently been down on power while making a high-pitched whining noise, the source of your burning oil might be a leaky turbo seal. This will also cause blue smoke in the exhaust and might throw a code with a check engine light. You can fix this with a partial rebuild for around $500 if you’re lucky. Otherwise, you’ll need to replace the turbo completely to stop the engine from burning oil.

Jason Farrell

Written By

Jason Farrell

Jason Farrell is a certified master technician, the editor of Mechanic’s Diary in Pittsburgh, Pennsylvania. He is ASE (Automotive Service Excellence) certified and earned a Bachelor’s Degree in Automotive Technology from Pittsburg State University. With nearly 18 prior years of experience in the automotive field, he has extensive knowledge about Domestic, European, and other foreign makes and models of cars and light trucks. Jason’s experience working as a technician and service manager at dealerships, gave him the experience and know-how of most aspects of inspection, diagnosis, and repair from engine and drivability to electrical, HVAC, brakes, steering and suspension and everything in between.

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