You’re driving down the road, and suddenly your oil light comes on — again! There's no puddle beneath your car, and you know it isn't time for another oil change. If you don’t see any visible signs of a leak, the issue may be something else entirely. Keep reading to learn why your car is losing oil but not leaking and what you can do to fix it.
Why Is My Car Losing Oil?
When a car mysteriously loses oil, there are usually two possible causes: either you’ve sprung a leak, or your engine is burning it away. Though you may not see any visible signs of leakage, less noticeable parts like a worn seal or leaky rings may be the culprit.
Fortunately, during a full-service oil change, Firestone Complete Auto Care offers a free 19-point inspection to find any visible leaks. But if you have to add a quart or more of oil to your engine between changes and there’s no leak to be found, chances are your vehicle's burning oil.
Low Oil But No Leak? You’re Probably Burning Oil
Oil burning happens when faulty engine parts allow oil to seep into the combustion chamber. Blue-tinted smoke coming from your exhaust is a potential indicator of this issue but may not always be evident if your engine only burns small amounts. While it’s normal for some cars to burn more oil than others, it’s best to have your vehicle serviced as soon as possible if you experience consistently low levels.
Losing too much oil can lead to serious engine damage and expensive repairs, especially among older cars with 100,000 miles or more on the odometer. However, vehicles with fewer than 50,000 miles should typically use no more than a quart of extra oil between changes.
Potential Causes for Burning Oil
When oil seeps into the combustion chamber, it’s usually due to one or more worn parts. For newer engines that use low-viscosity oil, such as 5W-20, even small amounts of wear can lead to oil entering this chamber. Here are a few of the common causes of excessive oil consumption:
Worn Out PCV Valve
The positive crankcase ventilation (PCV) system is a vital engine component that eliminates harmful gases generated during engine combustion. It does this by routing excess gases back to the combustion chamber, where they are burned a second time before exiting with the exhaust.
However, when the PCV system gets clogged, it can cause significant oil blowback. Rather than remove combustion gases, oil ends up getting sucked into the engine through the air intake. In most cases, resolving this issue simply requires replacing the PCV valve.
Worn Out Piston Rings or Cylinder Walls
Here’s where repairs can get pricey. Each set of piston rings forms a seal against the cylinder walls to maintain engine compression and prevent combustion gases from escaping. However, if your piston rings have worn out or the cylinder wall has begun to deteriorate, then the seal may no longer function properly. With a faulty seal, oil can enter the combustion chamber, burn, and leave you with less oil than you started with.
Worn Out Valve Seal
Faulty valve stem seals are another cause of low oil levels. While valve stem seals are meant to regulate oil consumption and valve lubrication, a broken one does just the opposite. A valve seal that has become worn or damaged may leak oil into the engine cylinders and eventually into the combustion chamber.
Don’t Let Burning Oil Burn a Hole in Your Pocket
Do you suspect a hidden oil leak or other oil problems? We can help. With a full-service oil change, you'll receive a 19-point inspection and an oil filter change. We'll even top off your window washer fluid, do an advanced oil leak troubleshoot using our detection with dye services, and check the levels of your car's other important fluids.
Head to your nearest Firestone Complete Auto Care or schedule an appointment online for all of your oil care needs today.
FAQs
If your engine is low on oil but there isn't a leak, that means it's probably being burned inside the engine. A bad PCV valve is a frequent culprit in the case of burning oil--but what is it, exactly? A PCV valve is designed to let air escape when the pressure in the crankcase is too high.
Why is my oil disappearing with no leaks? ›
When a car begins to lose oil but doesn't display any visible leaks, there could be several culprits at play. Common reasons include worn piston rings, a damaged head gasket, or an accumulation of oil in the engine's air-filtration system.
Why is my oil level going down but not leaking? ›
If you're losing oil but there's no leak or smoke, it could be due to several different factors. The most common is simply that your car is burning oil. This can happen for a number of reasons, such as an improper air/fuel mixture, worn piston rings, or excessive engine heat.
How do you fix an engine that burns oil? ›
How to Stop Your Engine from Burning Oil. Of the three main causes of oil burning, a bad PCV valve is the simplest one to fix. That's because the other causes – bad piston rings, cylinder walls, and valve seals – are not easy to fix at all, and often amount to an engine overhaul.
Is it normal to lose oil between oil changes? ›
It's normal for your engine to burn a little bit of oil between oil changes. Depending on the model and age of your vehicle, the engine might burn or consume up to a quart of oil between your regularly scheduled maintenance appointments.
Why does the oil in my car disappear? ›
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!
Why is my oil thinning? ›
Fuel contamination of the oil sump is another major cause of excessively thin engine oil. Both gasoline and diesel fuel are thinner than engine oil and when mixed, the oil's viscosity, film thickness and ability to separate parts are significantly reduced.
How do you fix low oil pressure? ›
You can increase your oil pressure by ensuring the oil level is within the manufacturer's recommended range, using high-quality oil that meets your engine's specifications, changing your oil filter regularly, keeping oil passageways clean, and making sure your oil pump is in good condition.
Does Lucas oil Stabilizer stop oil burning? ›
Lucas High Mileage Oil Stabilizer helps to control blow-by, dry starts and oil burning - maximizing efficiency, reducing harmful emissions and extending oil life. Lucas High Mileage Oil Stabilizer can also be used as an IDEAL ASSEMBLY LUBE.
Why is my car burning oil so fast? ›
Burning oil is often the result of worn-out parts. For example, worn valve seals and/or piston rings could lead to your car burning oil. Both valve seals and piston rings work to keep engine oil out of the combustion chamber.
Valve timing can. If the intake stroke starts and the valves are still closed, oil from the pan can be drawn into the cylinder past the rings, and it will mix with the'fuel/air mix and be expelled through the intake valve at the start of the compression stroke and the rest will be burnt by combustion.
Why is my car losing oil but no leak or smoke? ›
If your engine is low on oil but there isn't a leak, that means it's probably being burned inside the engine. A bad PCV valve is a frequent culprit in the case of burning oil--but what is it, exactly? A PCV valve is designed to let air escape when the pressure in the crankcase is too high.
Can bad spark plugs burn oil? ›
The short answer is no. Oil burn is caused by oil “leaking” into the cylinders past the rings or valves. Combustion then burns the oil. Things old spark plugs can cause is poor gas mileage, misfires/check engine light.
How much oil loss is normal? ›
Oil Consumption Rates Vary
During these conditions a consumption rate of one quart per 500 miles driven may be considered as normal usage. Some Chrysler applications reflect the following oil consumption rates: One quart per 2,000 miles for the first 50K miles.
Why is my bike losing oil but no leak or smoke? ›
It is probably burning the oil, but not enough to cause smoke. If its new it may be running in, if old the piston rings and/or cylinder bore could be worn. All engines burn some oil, some more than others.
Why is my oil life going down fast? ›
Under certain driving conditions (high temperatures, short trips, frequent starts & stops, and hilly terrain) your oil life will degrade faster than under normal conditions at lower RPMs.
Why is my car using so much oil? ›
Oil consumption is sometimes caused by mechanical problems. Seals and gasket, the bearings, cylinders, ring grooves, connecting rods can be worn or damaged. Cylinders that were not honed properly when the engine was built (or rebuilt), incorrect installation of the piston ring, or other improperly installed parts.
Does idling burn oil? ›
Idling your car or truck longer than is necessary causes it to burn more oil. The longer you let your engine run, the more motor oil circulates and burns. That means spending more money on more frequent oil changes. Excessive idling also decreases your car's performance.
