Put Too Much Oil in Your Car? (Here’s What Happens)

(Updated on August 25, 2021)

Inside an internal combustion engine, metal components move very rapidly, with tight clearances under intense temperatures and pressures. Without a source of lubrication, these components would quickly wear each other out from metal on metal contact. Engine oil is specifically designed to prevent this catastrophic wear.

Engine oil has a pretty tough job. It needs to be thin enough to allow the engine to start, yet thick enough to provide adequate protection at the engine’s operating temperature. 

When the vehicle is parked, the oil sits in the oil pan. Upon ignition, the oil pump switches on and sucks the oil up to start it circulating in order to lubricate all those moving parts. As the oil moves it passes through an oil filter, which collects any contaminants such as metal shavings that get picked up along the way. 

It is critical to have the right amount of oil. It is fairly common knowledge that too little oil can cause engine failure, but many people don’t know that too much oil can also cause major engine damage.

Consequences of Overfilling the Engine Oil

It’s always important to check the oil after it gets changed or after topping it off since the consequences of overfilling can be severe. Here is a list of problems you may experience from adding too much engine oil.

1) Engine Damage from Insufficient Lubrication

bad piston ring symptoms

It seems wrong, but overfilling the engine oil actually leads to reduced lubrication between the moving parts. This happens because the crankshaft sits above the oil pan in most cars and rotates quickly as the car moves.

If the engine oil level is high enough to touch the crankshaft, the crankshaft can whip the oil into a foam, similar to how a whisk aerates egg whites when you’re cooking something.

Frothy oil doesn’t lubricate well or move nicely through the system as it should. The oil flow can slow or stop completely which leads to overheating of the oil. If the engine isn’t lubricated properly parts will wear prematurely, and the engine may even seize up and stop running at all. 

2) Failing Seals and Gaskets

head gasket leak

When the crankshaft whips the oil, it introduces air into the oil which makes the volume and thus the pressure in the system increase.

Gaskets and seals are designed to hold a certain pressure of oil back from areas it’s not supposed to go, so over pressurizing it means that those are likely to give way. Some of these seals are difficult to access and replace, such as the front and rear main seals of the crankshaft.

3) Spark Plug Fouling

dirty spark plug

Excess oil can leak out and contact the spark plugs. Once oil coats the plugs, they may no longer receive the high voltage pulse that initiates the spark or the spark might not be able to jump the gap to initiate combustion. 

Fouled spark plugs can lead to engine misfires, running rough, or the vehicle may not even start. They are easy to replace should this problem occur. 

4) Fouled or Clogged Catalytic Converter

symptoms of a bad catalytic converter

The catalytic converter reduces the toxicity of exhaust gases. After the vehicle has been running, the catalytic converter is very hot. If any oil gets into the combustion chamber or farther in the exhaust system, it’ll likely burn up when it gets to the catalytic converter if it hasn’t already by then.

Oil burning in the catalytic converter will hinder the catalytic converter’s ability to clean exhaust gases and may shorten its life. Catalytic converters are expensive parts to replace.

In extreme cases, excessive oil could clog the catalytic converter. A clogged catalytic converter is a potentially dangerous situation as it could excessively hot and start a fire.

Symptoms of Excess Engine Oil

If you are experiencing any of these problems, stop driving as soon as it’s safe to do so, park on a level surface, and check the engine oil level. 

It’s best to check after driving for 5 to 10 minutes so that the car is warm and the oil has been circulating. The engine bay will have a dipstick you can pull out, wipe clean, reinsert, and pull out to check the level.

If the oil level is between the “add” and “full” lines, then you can rule out overfilled oil as the cause of your vehicle’s problems. 

1) Recently Added or Changed the Oil

excessive oil consumption

If you are completely certain that the oil level hasn’t been touched in the last few days that the car has been driven, then any other issues you experience probably aren’t from excess engine oil.

This is a problem that tends to show other symptoms within a few miles of driving. 

2) Blue Smoke

white smoke from exhaust

If you see a slightly blue tinted smoke coming out of the exhaust or engine (or if other drivers see it and wave you down), it is likely burning engine oil. This can also be caused by a leak dripping oil into the hot metal but could be because of excess oil.

3) Burning Smell

car smells

The smell of burning oil is pretty unique and acrid. If you smell it, there could be an oil leak or it could be seeping out onto hot engine parts. 

4) Leaking Oil

oil leak

As mentioned above, high oil pressure from too much oil can lead to failures in the weak spots, where oil can then drip out. You may see a puddle or little drips under your engine after the car has been sitting for a little while. 

5) High Oil Pressure Light

high oil pressure

Not all vehicles have an oil pressure indicator, but those that do may throw a “high pressure” warning if the engine oil has been overfilled. 

6) Running Rough, Stalling, and Misfires

engine misfire causes

These performance issues can be caused by spark plugs fouled when the excess oil contacts them. 

7) Car Won’t Start

trouble starting car

If the necessary spark for combustion can’t jump the gap in the spark plug because the plug is coated with engine oil, then the vehicle can’t start

8) Strange Behavior from Oil Gauge

oil pressure gauge

A dashboard oil gauge that swings back and forth between “add” and “full” may indicate overfilled engine oil.

The gauge is designed to work within normal operating conditions, so going outside of those can lead to a “confused” gauge. 

9) Overheating Engine

engine overheating symptoms

Insufficient lubrication between moving parts increases the friction between those parts, which generates heat.

If this is happening all over the engine when the foamy oil can’t do its job, the overall engine temperature might increase to damaging or dangerous levels. 

10) Noisy Driving

noise while driving

The sound of metal on metal can be very unpleasant. Very fast-moving parts contacting one another may generate a screech while slower-moving parts might sound more like a grind or groan. 

11) Difficulty Accelerating

car won't accelerate

This problem can be caused by greasy spark plugs or simply be a result of the car having to work harder to overcome the additional resistance of parts scraping, instead of sliding, past one another. 

How Much Oil Should There Be?

Of course the final dipstick reading should show a level between “add” and full, but it’s helpful to know how much oil this actually shows. 

In most vehicles, the total amount of engine oil is between 4 and 8 liters. It depends on the engine volume though, so check the owner’s manual for your type of car. 

Between the add and full line on the dipstick is usually about 0.5 to 1 liter. So if you need to add more oil, do so incrementally – about an eighth to a quarter liter at a time – to avoid overfilling.

It should be noted that a slight overfill probably won’t cause any problems. The slight excess oil should burn off after a few hundred miles. For instance, if the oil level sits a couple millimeters over the full line on the dipstick, you’re probably fine.

Removing Excess Oil

The good news is that it’s very easy (albeit a bit messy) to remove engine oil if you or someone else accidentally filled it too much. When you are checking the level during or after your oil removal, make sure you wipe off the dipstick before reinserting it to get a proper reading. 

If you have a siphon or fluid extractor, you can use the dipstick tube or fill tube to suck out some oil in a fairly neat and painless way.

Another way is to simply place a drain pan below the oil plug and loosen it very slowly with an oil wrench so that it just trickles out. Check the level frequently. 

If the oil hasn’t been changed in awhile and it looks dirty, you might just want to change the oil and oil filter while you’re out here. 

Conclusion

Even though overfilling the engine oil can have some serious consequences, it’s usually pretty easy to tell that something is wrong and to then diagnose and fix the problem. Anyone who is able to change their own oil at home can fix this for free if nothing has been damaged yet. 

20 thoughts on “Put Too Much Oil in Your Car? (Here’s What Happens)”

  1. I accidentally added some diesel to my petrol car and ran it with out any problem. However, a reduce oil level sign started show so I had all my fuel removed and the fuel lines flushed out , before adding fresh fuel. Again the car has been running fine but the reduce oil level sign is occasionally showing.
    Should I have the oil and filter changed now? I am mindful of damaging the engine which is a VW 1.5 TSI with less than 10k miles on the clock.
    What is confusing is that the car seems to run absolutely fine!

    Reply
    • I don’t know. How much is “some” diesel? Consider flushing the entire fuel system to be safe if you’re not sure. The peace of mind may be worth it to you.

      Reply
    • I once accidentally half filled my mg montego with diesel. It had a relatively early form of electronic fuel injection that adjusted the timing via an anti-knock sensor. This allowed tge car to run fine but unburnt diesel leaked past the piston rings and over filled the sump. The excess then burnt off filling the road with smoke every few miles. It took a few days to use up the tank but it cleaned the engine internals a treat. Changed the oil and filter and all was well again, lasted another 80k miles till i sold it on.

      Reply
  2. I was not aware my mechanic shop put a bit more oil during oil change. I only drive local & it was this way for 3 months. One day I found more oil in small puddle on passenger side & panicked. Another mechanic identified the issue & drained the overage of oil & told me it should resolve the many leaking areas by at least 70% Thankfully my car has been not shown any signs while driving it so hopefully it will correct itself JUST IN TIME & not be as expensive as first diagnosed!!

    Reply
  3. How can one mechanic place diagnose rack & pinion and transmission leaks when the leaks were all oil is what a more reliable mechanic told me.
    How can this be that 3 issues can really be just ONE?! Can oil leaks maybe mimic other leaks that are really not an issue??

    Reply
    • It seems like some shops are sorely lacking in diagnostic and troubleshooting skills. Engine oil and transmission fluid smell nothing alike, and only look similar if they are very dirty.

      Reply
  4. Hi there
    whilst driving along in my vehicle, we noticed a cloud of smoke coming from the rear end, car started over reving by itself, towed it to a mechanics to get a diagnostic check-came back with no codes showing however the oil was very overfill, but we are still not sure if that caused the issue. Could it have been? Our vehicle is diesel.

    Thanks

    Reply
  5. “Of course the final dipstick reading should show a level between empty and full, but it’s helpful to know how much oil this actually shows.” You mean the level should read between ADD and full.
    I put in 1 quart so my oil level is between empty and full. Should be fine LOL.

    Reply
  6. Can a leak from too much oil resolve itself after the amount of oil has been corrected? Or is this a sign of seal failure already and seals must be replaced?

    Reply
    • Yes, oftentimes bringing the oil level back down to the max line is good enough. If you see leaks at that point, you’ll have to start thinking about finding and replacing those seals.

      Reply
  7. I put too much oil in my car and it started revving at idle and the car felt very underpowered. For the first time since I’ve owned it I went pedal to the medal and I barely accelerated. When I changed the oil to a proper level I noticed a leak under the passenger seat part of the car but that has gone away. Car still feels very underpowered, what do you think?

    Reply
  8. My friend who shall remain nameless bought a Grand Prix at auction recently. A couple days ago it wouldn’t start and she asked me to add oil. First I checked the level and it was six inches over the full mark. The drain plug had been tightened by Superman and it took me two days to remove it. The drained oil overflowed a 12-quart pan! I put new oil and filter and then when trying to start, it would only “thunk.” After several attempts, it finally started and ran very rough for a few minutes before it smoothed out. Then I noticed that a huge white cloud of heavy smoke from the exhaust was hanging in the street. I shut it off immediately. This article and the comments explain what I was seeing. I believe the problem is solved and tomorrow will drive it in a rural area to burn any remaining residual oil and make sure that it running properly. I am hopeful that there is no further damage and will educate my friend about routine level checks and owner maintenance procedures. Many thanks to author Sean and all who added comments.

    Reply
  9. Just wanted to add if your oil level is at a good level be careful of additives and cleaners you might use and how much you’ve used. I didnt think my oil level was an issue but was having similar issues. My oil levels didn’t register to be a problem but i remembered I had added about a can and a half of sea foam to the crank case which in turn mixes with your oil and raider my oil level about 1/4″-1/2″ above full. Going to see if she’ll fire up now that i drained about a quart out.

    Reply
  10. Very important to be exact you could ruin a fairly new car before you even pay it off it’s like the right amount of vitamins and minerals in our bodies not to high and not to low it’s really important to be exact when you perform a simple oil change

    Reply

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