Too Much Oil in Car Engine: Symptoms & What to Do If You Overfilled It

Overindulgence is usually a bad idea. Anything in excess can be harmful, and everything in moderation is best. Still, most of us will recover just fine from a few too many drinks or a tough session at the gym.

As a machine, the average automobile doesn’t have the same ability, though. Too much or too little of anything (coolant, washes, driving, etc) can be damaging to your vehicle, especially if it’s being subjected to that on a regular basis. The same holds true for too much or too little oil in the engine.

That’s why every vehicle has its own set of specifications for many types of maintenance.

It’s important that we stick to these guidelines, or else we could end up causing more harm than good. After all, these guidelines exist for a reason.

Car owner with an open hood and filling up engine oil

Unfortunately, we know that accidents can happen even during the simplest chores. If your mind is wandering or you get distracted, you could make a mistake, and could end up paying for it in extra costs and time wasted down the line.

In this article, we’ll tell you all about what happens if you put too much oil in your car.

We’ll walk you through all the different symptoms that can crop up so you can identify them early, you’ll become aware of why ignoring them isn’t a wise decision, and you’ll know all about the different options you have to get your lubricant levels back to normal.

Symptoms That a Car is Overfilled with Oil

In this section, we’ll lay out some of the most common symptoms you need to keep an eye out for, ones that signal that you now potentially have an overfilled engine.

Some of these symptoms are non-specific. For example, an engine that runs loudly can have lots of potential causes, and that doesn’t necessarily mean that you’ve put excessive oil in your engine.

You also have to factor in the timing to make sense of what’s going on. If you’ve recently changed the oil, there’s a chance that too much lubricant could be the source.

There is a surefire way to know that your car is overfilled with engine oil, though. Take a peek under the hood and remove the dipstick. If you can’t see the fill line, there’s too much fluid in there.

Leaking Oil

The extra lubricant could escape or be forced out during engine operation. Black puddles underneath your vehicle could be a warning sign.

These puddles are also a hazard to the environment, and driving around with your car in this condition could get you in trouble.

Smoking Engine or Exhaust

Smoke (such as white smoke) coming out of the engine compartment or exhaust pipe is another symptom. Escaping oil will burn if it gets into contact with heated parts, producing blue-tinged smoke.

As with puddles, these unnecessary emissions aren’t eco-friendly. In certain states, it’s illegal to drive a smoking automobile.

Burning Oil Smell

This usually occurs alongside a smoking tailpipe or engine compartment. You won’t be able to miss the trademark acrid stink of burning lubricant.

Poor Performance

If the overfill isn’t addressed after a while, your engine performance may be impacted. This is typically due to foaming.

Surplus lubricant can get agitated by the crankshaft and other moving parts. This can only happen if the oil levels in your vehicle are too high.

Eventually, the viscous fluid will be transformed into a frothy foam, and the lightweight froth won’t be effective as a lubricant or a dispersant.

It will also contribute to inconsistent levels of oil pressure. All of these factors can provoke the following performance-related issues:

  • Noisy engine.
  • Misfires or stalling.
  • Trouble speeding up.
  • Frequent overheating (check our article on cars overheating if you experience this).
  • Difficulty getting the motor running.

What Happens If You Put Too Much Oil in Your Car? When Is It a Problem?

A millimeter or two over the fill line shouldn’t be anything to panic over, especially if this only happens once in a blue moon. On the other hand, several inches above the fill line is something to worry about.

A quart or more of unneeded motor oil in your car is a cause for concern.

Here’s what could happen if you keep driving with an overfilled reservoir:

Clogged Catalytic Converter

When there’s an excess amount of oil circulating, it’ll go places it shouldn’t. One such example is your catalytic converter, where it will burn.

This component wasn’t designed to handle fluids. If it ends up clogged, your motor won’t run smoothly.

After a certain point, your engine may even completely stop running.

Catalytic converters don’t come cheap, and replacing them isn’t easy.

Dirty Spark Plugs

Oil leaking can foul up your spark plugs. If you’ve bought new ones, you may have to chalk them up to a wasted investment.

Engine Damage

Remember that oil can be turned into foam when there’s too much of it, which could cause damage. Frothy lubricant is just as bad as not having any at all.

The foam can’t protect delicate mechanisms from friction damage.

Unstable Pressure

Foam has high quantities of air in it. As it circulates throughout your engine, it can destabilize oil pressure.

As a result, valve pipes can collapse and rods can be bent. The unstable pressure will also cause your motor to work harder than it has to.

No Cooling or Cleaning

Other useful properties will also be affected if the consistency is foamy. The bubbly liquid won’t work as well to disperse contaminants or dissipate heat.

Harmful corrosive substances can also build up in your engine. Sediment and debris will also build up, jamming up vital components.

Engine Failure

Foamy oil and the subsequent consequences can cause engine failure, which is certainly not something to be taken lightly.

This is the worst case scenario if you were to turn a blind eye to the symptoms we’ve covered so far.

What Can You Do When You’ve Overfilled Your Car with Oil?

So, you’ve established that there’s too much oil in your car, and it’s too late to go back in time and prevent that from happening. What can you do now? Is there any hope of remedying the situation?

The good news is that if you’ve caught it early, your car should be fine. Those of you with vehicles that are already showing signs of damage may not be so lucky, though.

If you fall into the second category, it’s advisable to take your car to a mechanic as soon as possible. The more time you spend sleeping on the situation, the more likely it is to become more difficult (and more costly) to deal with.

The solutions below won’t help if certain components are already affected.

For the rest of you who were lucky enough to have caught this problem early on, there are three strategies to choose from.

You can perform a draining, you can use an extractor pump from the comfort of your own home, or you can choose to just let your mechanic handle it. Let’s take a more detailed look at each of these 3 approaches in the following sections.

Drain Extra Oil

The car-savvy readers among you can attempt this at home all on their own. By doing this, the goal is to return oil levels to normal without draining everything in the reservoir.

To do this, you’ll need the standard equipment:

  • Safety glasses and gloves.
  • Appropriate wrench for your drain plug.
  • Jack and vehicle jack stands.
  • Drainage pan.

Step 1

Make sure the engine is cool before you begin. If not, allow up to an hour or more for it to cool off.

You may not be performing a full drain, but you can still get scalded. Put on your gloves and adjust your safety goggles.

Step 2

Jack your car up and place the jack stands so that it’s secure.

Step 3

Position the drainage pan underneath the drain plug. Do so carefully — in case you lose control, you don’t want things to get messy.

Step 4

Here’s the difficult part: You’re going to gradually loosen your oil plug without removing it completely.

To do so, use your wrench as carefully as possible — you don’t want lubricant to come gushing out. You’re aiming for a slow trickle. Monitor the flow carefully until you feel like a sufficient amount of fluid has drained out.

Step 5

Tighten your plug back up. Now, it’s time to check the oil dipstick to see if you can spot the fill line, or if you’ll have to try again.

Using an Oil Extractor Pump

If you have a well-equipped home garage, you may have oil pumps.

If you decide to go down this route, you’ll also need these items:

  • An old rag or towel.
  • One clear container (preferably with measurements marked on it).
  • Gloves (this is optional).

Step 1

Allow your engine time to cool off if you were driving. Warm oil is fine to work with, but it shouldn’t be boiling hot. Put your gloves on if you want to keep your hands from getting dirty.

Step 2

Pop the hood of your car and take out the dipstick. Place it on the rag or old towel to protect surrounding surfaces from stains.

Step 3

Set up your extractor as per manufacturer instructions. Connect it to a power source (e.g. your battery) and prepare the tubes and drainage container.

Step 4

Insert the extractor tube into the dipstick tube. Power up your machine and keep a close eye on the container.

Once enough fluid has been removed, switch off the machine. You may want to check the fill line every so often to make sure you haven’t removed too much.

Step 5

Once you’ve checked the oil level and it has returned to normal, disconnect the extractor. Replace the dipstick, and you should be good to go.

Getting Professional Help

In some cases, it could be that your mechanic is the one responsible for overfilling engine oil.

In these cases, the garage likely won’t charge you to remove excess oil. You may also want to bring it to their attention to avoid a repeat incident, whether that’s with you or any other client that goes to that shop for car maintenance purposes.

Even if you were at fault for overfilling your car with oil, you might still want to go to a mechanic anyway to get the problem fixed.

Perhaps you don’t own an extractor, maybe you’re worried about wasting lubricant by draining it, or perhaps you don’t want to deal with a mess at home. Either way, heading to a professional for help might the best alternative for many people.

What to Avoid Doing When Removing Extra Oil

You may have thought of a few other tactics we haven’t mentioned, but the creative route isn’t always a good idea.

Some techniques can be dangerous for you or your car, and it’s almost always best to stick to the tried and tested methods that have been proven to work well and be safe.

Non-Automotive Vacuum or Equipment

Don’t try forcing a syringe down the dipstick tube. If the needle breaks off, you’ll have a whole other problem on your hands besides too much oil in your car.

Similarly, using a rigged vacuum or another homemade gadget isn’t advisable. You’re more likely to end up breaking the device you’re using or making a mess.

Mouth Siphon

Never attempt siphoning oil out with a tube and your own mouth.

A mouthful of petroleum byproduct is not only disgusting, but can make you very sick too.

Conclusion

If you’ve made it this far, you now understand what happens if you put too much oil in your car.

Again, bear in mind that several ounces worth shouldn’t do any harm, especially when it only happens so infrequently. However, one or more quarts of oil could have major ramifications, especially if it happens too often.

All of the long-term effects of driving a car that’s overfilled with oil are serious. Insisting to push your vehicle’s engine to the limit can result in total failure, and will end up costing you loads of money and wasted time on repairs down the line.

Taking action early on will cost you less than an hour or a (relatively) small fee to your mechanic. Wait too long to address the situation, and you might have to shell out hundreds or even thousands of dollars for repairs.

If you accidentally have an engine oil overfill, don’t be too hard on yourself – now isn’t the time for that. It happens with even the best of us, and your sole focus right now should be fixing the problem as soon as possible.

You also shouldn’t be discouraged from continuing to change your car’s oil on your own. We all make mistakes, even certified mechanics – we live, we learn!

Kyle Palmer

From childhood go karting and motocross, to collecting and obsessing over scalextric, matchbox and radio controlled cars, I've always had an obsession with cars. Learning through manuals, books, trial and error, and more knowledgeable family members, I've also enjoyed tinkering with the mechanics and electronics of any vehicles I've owned. Now, over 3 decades later, I've started this site as a place for me to share my knowledge, to teach others how to care for and maintain their vehicles themselves, at home, so they can get the most of their vehicles and save a pretty penny compared to always seeking out professional help.

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