You’re no doubt already familiar with engine oil and what it’s used for. As we’re sure you know, engine oil is used as a lubricant for all of the moving parts of your car’s engine, which helps prevent these parts from becoming damaged. All engines have a minimum amount of oil they need in order to function properly.
While you’re probably already aware that too little oil is bad for your engine, you might not know that too much oil in your car is also bad. If you drive your car for too long with too much oil in the engine, you risk severely damaging or even totaling your engine.
In this article, we’ll be going over why an excess of engine oil is so bad for your car, the symptoms you should look out for if you suspect that your engine oil has been overfilled, how to deal with overfilled engine oil, and other things about your engine oil that you may want to know.
Why Is Too Much Oil Bad for My Car?
Too little engine oil is never a good thing to have, but too much engine oil can be equally as bad, especially if your oil pan is really overfilled. If you leave too much oil in the engine for a long time, it can potentially cause the following problems:
Flooded Spark Plugs
Spark plugs are a vital component of your engine, for without them, your car wouldn’t have the means to ignite the fuel in its cylinders. Spark plugs need to be clean in order to work properly. When spark plugs are really dirty, the spark is unable to jump between the two electrodes of the plug.
If you put too much oil in your engine, it can leak out and cover your spark plugs, leaving them fouled. Fouled spark plugs have their own set of symptoms, including reduced gas mileage, engine misfiring and rough idling, and reduced engine power.
Bad Catalytic Converter
The catalytic converter in your car isn’t as essential a component as your spark plugs are, but is still quite important. The catalytic converter helps reduce the amount of toxic gasses and other pollutants in your engine’s exhaust. If you have a smog test coming up, you’ll need a working catalytic converter in order to pass.
Related: How To Tell If a Catalytic Converter Is Clogged
If you’ve overfilled your engine with oil, there’s a chance that some of it will make it through the combustion chamber and end up burning inside the catalytic converter. If this happens for a while, it can significantly reduce the lifespan of the catalytic converter.
In severe cases when a lot of oil manages to get into the catalytic converter, it can end up causing an oil fire, which is both bad for your car and a major safety hazard.
Damaged Engine Components
You might think that it’s better to have too much engine oil than too little. After all, oil is a lubricant, and if you have moving parts that need to be lubricated, it’s better to have more lubricant than less, right?
Well, in the case of engine oil, this is definitely not true. In fact, putting in too much engine oil can actually decrease its ability to keep the engine lubricated.
The engine oil sits in the oil pan, which is located directly below (and completely exposed to) the crankshaft, which spins around very fast. If you overfill your engine with oil, it can come into contact with the crankshaft, which will actually whip the oil into a frothy, air-filled state.
Frothy oil isn’t a very good lubricant and doesn’t move through your oil lines very well. Slow-moving oil also heats up more quickly, and overheating your engine oil will cause it to degrade and lose even more of its effectiveness.
Ineffective oil isn’t going to provide your engine parts with the lubrication they need. By running your engine with too much oil you risk damaging various components in your engine or causing your engine to completely seize up.
Blown Head Gaskets
If the engine oil has been whipped up into foam by the crankshaft and contains more air than normal, this causes the internal pressure in the oil system to increase. This can put a lot more strain than normal on your engine’s head gaskets.
The head gaskets are responsible for keeping your engine sealed and airtight, which is necessary for proper fuel combustion and to prevent oil and coolant from getting into the cylinders. Having a blown head gasket will result in a variety of different problems.
Symptoms of Too Much Oil
Luckily, if you have indeed overfilled your engine oil, it’s usually pretty easy to diagnose the problem. There are several symptoms associated with an excess of oil in your engine. Let’s go over some of these symptoms now.
Remember: If you overfill your engine with oil, it can come into contact with the crankshaft, which will actually whip the oil into a frothy, air-filled state.
Blueish Smoke From Your Exhaust
If there’s engine oil burning in your exhaust, one of the most obvious signs of this is blue-gray smoke coming from your exhaust pipe. Only burning oil produces this color of smoke, so if you happen to see it, you can pretty much guarantee that oil is getting into your exhaust from somewhere.
It’s worth noting that this problem can also be caused by an oil leak as opposed to overfilled engine oil, but in any case, if you notice blue smoke coming from your exhaust it means that oil is getting in there somehow.
Visible Oil Leaks
If the excess oil pressure in your system causes your head gaskets to blow out, the oil will start leaking from the places where the gaskets have failed.
If you notice small puddles or drops of oil under your car after it has been sitting for a while, it could be a sign that your head gaskets have failed. You may also want to inspect your engine where the cylinder head meets the engine block, as this is where the head gasket is located. If you see oil stains around this area, your head gaskets are probably leaking.
The Smell of Burning Oil
If you smell burning oil, it’s a sure sign that oil is leaking out from somewhere and coming into contact with some of the hot engine parts. The smell of burning oil is pretty distinctly acrid, and you’ll definitely know it if you smell it.
Overheating Engine
Engine oil provides lubrication to your engine’s moving parts, which helps reduce friction and in turn keeps the engine temperature low. As you know, friction generates heat, and too much friction will cause the engine to overheat.
Unusual Engine Noises
Aside from heat, friction also generates noise. If you have two pieces of unlubricated metal moving against each other at high speed, you’re most definitely going to hear it.
Related: Why Your Car’s Transmission is Slipping & Fix
Depending on how quickly the pieces are moving against each other, the sound you hear might be a metallic screech or a groaning/grinding noise.
High Oil Pressure Warning
It’s not so common for cars to have an oil pressure gauge anymore, but if your car does happen to have one, it can help you determine if your car is overfilled with oil.
Excess oil in the system will result in increased oil pressure, so if your oil pressure gauge is giving you a particularly high reading, this could be the reason why.
Related: Is Driving With a Bad Oil Pressure Sensor a Good Idea?
How to Deal With Too Much Oil
Fixing an engine that has been overfilled with oil is actually pretty easy, especially if you catch it before actually driving your car anywhere. Putting too much oil in your engine won’t damage your engine on its own; it’ll only damage your engine if you actually drive around with too much oil.
There are two ways you can remove excess oil from your engine.
- Drain Plug: The first way is to simply open the drain plug on your engine’s oil pan and let the excess oil drain out. This way is pretty simple, but you’ll have to raise your car up in order to access the oil pan, and draining the oil this way can be a bit messy.
- Oil Extractor Pump: The second way is to use an oil extractor pump to remove the excess oil. Oil extractor pumps let you remove excess oil through either the dipstick tube or the oil cap. This way is a little cleaner, and you also don’t have to raise the car up to do it.
Engine Oil FAQs
Below, we’ve compiled a short list of some of the other questions you might have remaining about your engine oil.
Is It OK to Slightly Overfill My Engine Oil?
The correct amount of oil for your engine depends on the kind of car you have, although in general, most car engines need about 5 to 8 quarts (4.7 to 7.5 litres) of oil.
If you add an extra quart or more, then you’re definitely at risk of damaging your engine, but if you only put in an extra eighth of a quart or so, you should be fine.
Some engines are more sensitive to being overfilled than others, however, so in any case, it’s always a good practice to avoid overfilling your engine oil.
How Do I Check if My Oil Has Been Overfilled?
The easiest way to do so is to check your dipstick. Your dipstick has indicators telling you what the minimum and maximum oil level in your engine should be, so it’s pretty foolproof.
If you see that the oil is well above the maximum fill line on your dipstick, there’s probably way too much in there and you should drain it. If the oil is only a millimetre or two above the maximum fill line, however, it’s probably still within acceptable limits.
It’s a good idea to check your oil levels whenever you take your car in to get serviced. It’s unlikely that the shop or dealership will vastly overfill your engine oil, but it never hurts to be cautious.
Will Excess Oil Burn Off?
Excess oil can burn off, but only if there’s a very small amount of excess oil. In general, oil levels stay pretty consistent throughout the oil’s lifespan. If you’ve severely overfilled your engine with oil, not nearly enough if it will burn off to make a difference before your engine is damaged.
How Much Does It Cost to Deal With Overfilled Engine Oil?
If you catch the problem early enough, it might not cost you anything at all. Draining excess oil yourself is pretty easy and can be done at home with very little equipment.
If you leave too much oil in the engine for long enough that it becomes damaged, however, that’s a different story. Repairs like head gasket replacements are pretty expensive, and repairing a severely damaged or seized engine can easily run you thousands of dollars.
