It may not be common knowledge that most new cars consume oil even if they have less than 50,000 miles on the clock. Still, to know if that’s the case, you need to know how much oil consumption is normal, which we will discuss. On the other hand, if you have an older car or the oil consumption is alarmingly high, here is what the possible causes are before we go into more detail.
A car losing oil but no oil leak or smoke could mean a couple of things, including a clogged PCV valve, worn-out valve seals, and worn-out piston rings, but again, it could just be normal consumption common in modern engines.
Car Burning Oil Symptoms
A car burning oil symptoms are pretty straightforward. You will notice that engine oil is frequently low on the dipstick or a low oil warning light coming on at least once a month. But the most obvious sign that the engine is burning oil instead leaking is exhaust smoke.
Specifically, blueish, grey, or white smoke. But keep in mind that exhaust condensation is also white, so it’s important you don’t confuse the two. Condensation will be most obvious when it’s cold outside, and it starts coming out a minute or two after you start the engine.
And another giveaway that the engine is burning oil is the smell. Burning oil has a specific and hard-to-describe smell, but it’s still undeniably a burning odor. And lastly, some more subtle symptoms include poor performance, fuel economy, and a check engine light coming on intermittently or it stays on permanently.
What Causes Car Losing Oil But No Oil Leak or Smoke
Most of the causes of a car losing oil but no oil leak or smoke are pretty simple to check and test. That’s all except worn-out piston rings. But here, we won’t talk about testing, inspection, or fixes and instead will focus on additional symptoms and explain why each problem happens.
Clogged PCV Valve
The PCV valve is a pretty simple spring-loaded valve that’s controlled by an intake manifold vacuum. The purpose of a PCV valve and system is to lower the crankcase/oil pan pressure when the engine is running. When the pressure is high, the PCV valve opens and lets the excess pressure into the intake.
However, the PCV valve and its hoses are prone to clogging. Those oil vapors that pass through the PCV valve can leave sludge behind that either clog the hoses or seize the valve itself. Now, when that happens, the crankcase pressure builds up, and a small amount of engine oil enters the combustion chamber, where it burns.
So, technically a clogged PCV valve will lead to oil burning, but there won’t be any exhaust smoke because not enough oil will burn to produce it. But some other symptoms you might notice are misfires, check engine lights, and sludge build-up in the intake and valve cover. And this is what causes oil to disappear in the engine most commonly.
Worn Out Valve Seals
Valve seals rarely fail, and they do; it’s on an engine with at least 100,000 miles. Still, things can happen. Now, the valve seals are essentially just smaller oil seals that sit around the engine valve stems. And like all rubber seals, they degrade with time and start leaking.
So, the most obvious sign the valve seals have failed is exhaust smoke, which I know isn’t the subject but hear me out. The valve seals will only make a short and quick puff of blueish or white exhaust smoke right when you start the engine. Once that puff is done, you won’t notice any more smoke, which makes it fairly difficult to notice, and that’s why valve seals are on this list.
Some other valve seal symptoms include misfiring, a lean air/fuel mixture, a check engine light, rough idle, and it could be more difficult to start the engine. More specifically, you have to crank the engine a couple of seconds longer than usual.
Worn Out Piston Rings
The piston rings are the only sealing component between the piston and the cylinders. That means piston rings are the ones sliding against cylinders; they hold compression, lubricate the cylinders with built-in oil passages and keep oil in the oil pan from entering the combustion chamber.
Naturally, even in a well-maintained vehicle, the piston rings will wear out eventually, but it rarely happens before you reach at least 150,000 miles. And, of course, it can happen a lot sooner if the engine has factory defects or if it is poorly maintained.
So, when piston rings wear out, oil in the oil pan will enter the combustion chamber and burn, but you won’t notice any exhaust smoke early on. What you will notice is missing oil, possibly a check engine light, and a noticeably increased fuel consumption combined with poor performance. Also, the car will fail a compression test.
It Could Be Normal Oil Consumption
It’s common for a lot of normal cars to burn oil, and it’s even specified by the manufacturer. You can find such information in your owner’s manual or contact a local dealer to see if that’s the case with your car. But as an example, Audi specifies that it’s normal for its TFSI engines to consume up to one quart of oil every 1,200 miles.
That amount is far from neglectable and is usually a cause for concern in most cars, but the point is that such cars exist. On the other hand, if you have a brand new car, it’s normal if it consumes oil in the first 10,000 miles or so. That happens because all the moving parts inside the engine are not broken in yet, and among other things, the piston rings are not sealing properly.
How To Stop Engine From Burning Oil
To stop an engine from burning oil, you first have to figure out why it’s burning it in the first place. So, to do the inspections properly and most efficiently, go over the following fixes chronologically. Under each, you will also find the cost of fixing it and how to test it. So, here is how to stop the engine from burning oil, depending on what’s causing the problem.
Normal Oil Consumption
To check if your car is losing oil naturally, first, monitor how much oil it’s losing. The easiest way to do it is to top it off, do 1,000 miles, and see how much oil it lost as you top it off again. Then, check your owner’s manual to see if oil consumption is normal for your car, or contact a dealer.
Whichever option you choose, you will learn exactly how much oil consumption is normal in your car, and if it’s more than that, take it for an inspection or follow the rest of our instructions. On the other hand, if you have a brand new car, wait at least until it gets the first oil change or until it passes 10,000 miles until you start worrying about oil consumption.
Clogged PCV Valve – Inspection and Fixes
Before trying to fix anything, here is a simple way you can check if the PCV valve is working properly. The only thing you will need is a standard latex glove. Now, take the glove and cut one finger off. Then, remove the oil dipstick and put the glove finger over the dipstick hole so that it seals properly all around.
After that, have someone start the engine, and if the glove finger starts inflating, the PCV valve is clogged. However, if the glove finger starts to get sucked in, the PCV valve is good. Also, make sure the dipstick tube doesn’t suck in the latex finger, so hold it with your hand at all times.
And if the PCV turns out to be faulty, a new one will set you back around $15 to $20 plus roughly $50 for labor. And while you are at it, it doesn’t hurt to replace all the PCV valve hoses since they are pretty cheap as well.
Worn Out Valve Seals – Inspection and Fixes
To check if the valve seals are faulty, have someone start the engine while holding the throttle wide open. At the same time, you should monitor if any smoke blows out the exhaust just as the engine fires up. Also, instruct your friend to release the gas pedal when the engine fires up. It’s also preferable for the engine to be cold prior to this test.
And needless to say, if there is a puff of white or bluish smoke, the valve seals are bad. If that’s the case, new valve seals will set you back around $50 to $100 for a full set. However, labor costs won’t be so cheap. On the low end, you will pay at least $200 for labor and up to $1,000, depending on the model. That brings the total car burning oil repair cost, in this case, to a not-very-realistic $250 on the lower side and a more realistic median cost of $450.
Worn Out Piston Rings – Inspection and Fixes
Piston rings are by far the most expensive thing to replace on this list, but luckily also the least likely problem. To check if piston rings are bad, you need to perform a compression test using a special tool you can find on Amazon for $20 or have a professional do it for around $50 to $100.
And if the compression is lower than what the manufacturer specified, the only thing that can be wrong under the circumstances we are discussing is the piston rings. Unfortunately, it’s nearly impossible to estimate how much replacing the piston rings will cost. Still, we can say that it will be at least $800, but more likely closer to $1,500 or more.
The alternative here is to drive the car and keep adding oil until it stops working, which can happen in a couple of months or a couple of years. And the second alternative is to buy a used replacement engine. However, that, too, cost roughly $1,000 all in.
FAQs:
Q: Why is my oil disappearing with no leak?
If your oil is disappearing without a leak, it means the engine is burning oil. That means oil is getting into the combustion chamber, which can happen if the engine has worn-out piston rings, leaking valve seals, or a faulty PCV valve. That said, it’s normal for some modern cars to burn oil naturally. So it’s a good idea to check if that’s the case for your specific model.
Q: Why does my car burn oil, but it doesn’t smoke?
If a car burns oil but doesn’t smoke, it means the piston rings or valve seals are worn out, or it could mean that the PCV valve is clogged or faulty. Essentially the causes are the same as if smoke was coming out of the exhaust, only in this case, the piston rings or valve seals are not as worn out if that’s the cause.
Q: How much oil loss is normal?
For cars that don’t consume oil from the factory, anything over one quart of oil between oil changes is reason enough to get an inspection. However, most modern cars consume as much as one quart of oil every 1,500 miles, and manufacturers consider that normal.
Q: Can a bad spark plug burn oil?
No, bad spark plugs don’t cause the engine to burn or lose oil. The correlation between burning oil and spark plugs is that you can check if the engine is burning oil by checking if the spark plugs are greasy and wet. And if they are, it means oil is getting into the combustion chamber.
Q: Does synthetic oil burn faster?
No, synthetic oil doesn’t burn faster than synthetic blend and especially not faster than conventional. Full synthetic oil has much better lubrication and heat-dissipating properties since it’s an entirely man-made lubricant, with those properties set as the number one priority.
Q: Is it normal to lose a quart of oil?
Whether or not it’s normal to lose a quart of oil depends on how fast the engine consumes it. For certain modern engines, losing a quart of oil every 1,500 miles is considered normal, but the manufacturer has to specify that. Otherwise, losing more than a quart of oil between changes is already considered high.
Final Words
Ultimately, a car losing oil but no oil leak or smoke can mean one of four things, with the most common one for newer drivers or new car drivers being that the engine is a natural oil burner. That means the engine consumes oil from the factory, which is anywhere up to a quart every 1,200 miles. However, you should contact your dealer to see if that’s ok for your specific car.
However, if your car has just recently started losing oil without showing any leaks or exhaust smoke, it can mean that the PCV valve is clogged or stuck closed, that the piston rings are worn out, or that the valve seals are leaking.
