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Too Much Oil in Your Car: Symptoms, Effects, and What to Do

Changing your vehicle’s oil is one of the most common and easiest automotive-related tasks that just about anyone can accomplish. Even still, mistakes can be made by anybody, and adding too little or too much oil are both potentially severe mistakes.

When too much oil is added, your engine could have several major consequences if not taken care of immediately. Several signs and symptoms, including the oil dipstick indication level, blue exhaust smoke, leaking oil, and even an engine misfire, can all be signs of oil overfilling.

Fortunately, fixing the issue is not nearly as hard as one might think if caught early, but if overfilling signs are ignored, it could mean a new engine in the worst-case-scenario.

How Much Oil is Too Much?

too much oil in car

The amount of motor oil each vehicle needs varies from vehicle to vehicle depending on the manufacturer and engine size. Engine size is usually more of an indication of how much oil a vehicle needs since smaller engines require less oil than larger ones.

The easiest way to know for sure how much oil your specific vehicle needs is to look in your owner’s manual. If that is not available, most manufacturers post this information on their respective websites, or you can often go to specific make and model forums to find the information you need.

Generally speaking, vehicles can take anywhere between five and eight quarts of oil.

What Can Happen if You Put Too Much Oil in Your Car?

Oil is necessary for a vehicle with so many different moving parts. The correct amount must be used. Too little oil is a well-known cause of engine problems or failure, but too much oil is often an overlooked problem. Several issues could occur if too much oil is added to the engine.

Frothy Oil

Oil added to a vehicle travels down the fill tube and into a reservoir called the oil pan. If filled too much, the pan will “overflow” and allow the oil to reach moving components of the engine it is not meant to contact.

Even though it is pumped through the engine to lubricate its parts, oil that contacts the crankshaft can be churned up like milk in a frothing machine.

This can have the opposite effect of its intended purpose and not lubricate needed parts due to this aeration process. This frothing causes oil to lose its lubricity, and thus, its effectiveness.

Too Much Pressure

An engine and its moving parts are sealed so that things like water cannot get in and interfere with engine balancing or cause worse damage. As a result, many areas within the engine contain immense pressure.

Read More: The Reasons Behind High Oil Pressure

Likewise, the systems that pump oil to needed parts are also pressurized. The increase in oil volume can also lead to an increase in component and overall engine pressures.

This may not be a problem in the short-term, but it will certainly lead to detrimental issues if not addressed.

Leaking Oil

One of the direct results of increased engine pressure is oil leaks. An engine is not comprised of one huge piece that contains each moving part, but rather, it is made up of thousands of components that are sealed with gaskets and bolts.

Increased engine pressure can cause the gaskets to reach beyond their limits and slowly leak or burst. The result could be as small as a drip on your garage floor that is hardly noticeable to a large puddle of oil on the floor and all over the engine. 

Spark Plug Issues

Two things generally cause spark plug issues: age or fouling. Age affects nearly everything, but sparkplug fouling is often a result of excess fuel or oil that doesn’t all get burned by the combustion of the engine.

As a result, spark plug issues caused by excess oil are usually the result of prolonged oil leaking and not rectifying excess oil issues over a longer time. This can be an even more serious issue than leaking since spark plug problems can also cause serious issues by themselves.

In addition to being an inconvenience, sometimes causing a vehicle to not start, spark plug fouling can also cause fuel mileage to drop, engine misfiring, and even the engine to completely stop while driving.

Catalytic Converter Issues

Your catalytic converter is important because it filters contaminants from the exhaust that would otherwise be dispelled into the atmosphere. Its work lends itself to becoming clogged though, and burning excess oil hurries this process.

When the catalytic converter becomes clogged up, it can cause the check engine light to illuminate, make the vehicle run poorly, and cost a lot to replace.

How Do You Know if You've Put Too Much Oil in Your Car?

There can be many different ways to know whether or not you have put too much oil in your vehicle. The good part is that many of the most obvious signs can help catch the issue before more serious signs start to signal greater damage.

Dipstick Measurement

dipstick check

The simplest way to check whether you have put too much oil in your vehicle is to check the oil dipstick by opening the hood, unscrewing the cap, and looking at the oil mark.

The dipstick is usually used to show if you have too little oil in your vehicle or if the oil needs to be changed, but there are markings on the dipstick that indicates a desired oil level range. 

Oil Leaks

Leaks go hand-in-hand with the excess pressure that can result from overfilling the oil. It may not be obvious to you how high the oil pressure within your engine is, especially if you do not have a gauge in your vehicle, but the seals and gaskets in your engine can make it obvious.

Any part of the engine that attaches to another part, any hoses sealed with clamps, and any joints are the likeliest spots to find a leak. 

Smell

Oil is a strong substance with a distinct odor. If it is leaking enough, the smell will become obvious, especially if you park your vehicle in a garage.

Leaking oil does not just drip on the floor though. Any leaking can also occur at different points within the engine, and if a leak occurs above a hot surface, you may also smell burning.

Regardless of the root cause, the smell of burning oil is not normal in a vehicle and should be addressed immediately.

Oil Pressure Gauge Indication

Many vehicles have an oil pressure light that illuminates if there is an issue with the pressure. Some even have a gauge that shows the exact oil pressure gauge at any given time.

If the gauge is reading too high or the warning light comes on, you should find a mechanic to diagnose the issue. It may not always be a result of overfilling, but it could be, especially if this occurs shortly after an oil change.

Blue Exhaust Smoke

Normal vehicle exhaust is usually clear and unnoticeable. Sometimes, when the weather becomes colder, you can see it because of the heat, and diesel vehicles often emit black smoke when too much fuel is being fed to the engine.

Blue exhaust smoke is a sign that oil is being burned with the fuel. This usually signals an oil leak that is causing it to get into the combustion chamber, a place it should not be found in large quantities.

Unlike the oil pressure light, blue exhaust smoke is often a relatively early sign that something is wrong.

Engine Starting and Running Issues

Another result of oil leaking and fouling the spark plugs is engine starting and running issues. Both starting and running require that the air and fuel mixture within the engine is properly ignited to move the pistons and make the engine turn.

When a vehicle’s spark plugs are hindered from firing on time, or at all, a vehicle may not be capable of starting or running. Unfortunately, in the worst-case-scenarios, this could also cause a vehicle to stall while driving. 

Overheating

An overheating engine is one of the worst-case-scenarios caused by overfilling your vehicle with oil. If the oil is churned up by the crankshaft, it starts to foam and loses its lubricity, the moving components within the engine will not be able to run smoothly.

This creates a buildup of friction which also causes a buildup of heat. A one-time overheating moment will likely not cause too much damage if caught quickly; however, if left alone, engine components will begin to break down and even melt, resulting in the need for a new engine.

How Do You Fix an Overfilling Issue?

draining oil

Fixing an overfilling issue is quite easy if caught early. You will need to find the drain plug and release any excess oil just as if you were letting out the old oil to change it in the first place.

The fix becomes more complicated depending on how bad the other signs and symptoms of overfilling become. If you have questions about the things you hear, see, and smell from your vehicle when overfilling is suspected, take your car to a mechanic to find out what needs to be done before greater damage occurs.

Conclusion

Even though changing the oil in your car is one of the more mundane tasks of the automotive world, mistakes like overfilling can happen.

Losing its lubricity because of frothing, increased engine pressures, and leaking are all results of overfilling. Looking at the dipstick or smelling oil that has leaked are both easy ways to catch this issue, but other signs like blue exhaust smoke and engine overheating can also be signs of overfilling.

If caught early enough, you can fix the issue by letting the excess oil drain from the drain plug under your vehicle. If not caught in time, major engine damage could occur and fixes could vary depending on the extent of the damage.

Shawn Furman
I have been a vehicle hobbyist for as long as I can remember as well as a freelance writer for the past three and a half years. My clients have included Vehicle Scene, Autolist, CarGurus, and now The Vehicle Lab. In addition to my current clients, I also maintain my own blog where I am able to share my knowledge and experience through vehicle reviews, car-buying guides, how-to guides, and list articles.
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