Engine Oil

What Happens if You Overfill Auto Oil?

Routine oil changes are a preventive maintenance item usually performed several times throughout a year, depending on how often you drive. Whether you are brand new at DIY oil changes or a veteran, accidents happen, and an excess amount of oil could be poured into the car. You may be wondering: ‘What happens if you overfill auto oil?’

Automotive oil reservoirs are designed to hold a bit of extra oil to compensate for fluid expansion in warm conditions and help prevent damage to the engine if excessive oil is added. As a result, half a quart may not cause any damage to your engine, but much more than that could lead to engine damage.

When too much oil is poured into the reservoir, the excess oil can be pulled into the crankshaft as it spins. The oil is mixed with air and aerates – also known as ‘foaming’ – like what you might find on your morning latte. The combination of oil and air results in decreased oil pressure as the oil pump cannot continue pumping the oil effectively.

Can Too Much Oil Damage Your Engine?

In a word, yes. Several things might happen if a significant amount of excess oil is added to your engine. Your engine relies on consistent oil pressure to keep the moving parts running smoothly. Changes in the oil pressure and overall lubrication of the engine can lead to:

  • Engine damage such as bent rods in the engine or collapsed valve pipes.
  • Catastrophic engine failure where the engine sustains enough damage that it cannot be repaired but must instead be replaced.
  • The excess engine wears from inconsistent oil pressure over time.
  • Spark plug fouling, resulting in replacing spark plugs more frequently.
  • Excess oil deposits in the catalytic converter.

As you can see, adding too much oil to your engine can cause various problems. But if there’s already an excess amount of oil in the reservoir, what do you do?

My Car is Overfilled with Oil – Now What?

When your car has been overfilled with oil, the most important thing to do is to drain the excess amount in the reservoir before you drive the vehicle again.

Overfilling your car with oil is a relatively easy problem to fix if you have the right tools. You’ll need to drain the oil out of your car or have someone do it for you.

If you haven’t filled your oil yourself, you may not immediately realize that your car has been overfilled. It’s a good rule of thumb to check your dipstick after leaving your mechanic or oil change shop. If the oil level on the dipstick is an inch or more above the recommended fill level, then your car has been overfilled and should not be driven again until the oil has been drained from the vehicle; otherwise, you could cause serious damage to your engine.

Engine Oil Overfill Symptoms

It’s one thing to correct the problem if you’ve performed the oil change yourself and know you’ve accidentally added too much. But what if you took your car to a mechanic or oil change shop? Knowing the most common engine oil overfill symptoms will help you prevent damage to your vehicle.

Common signs of engine oil overfill include:

  • Oil leaking from your car
  • The smell of burning engine oil
  • Smoke from the engine compartment
  • Smoke or black exhaust from the tailpipe
  • Unusual noises coming from the engine

These symptoms can overlap with other engine issues, so it’s a good idea to visit T3 Atlanta if you notice any of these symptoms. We are full-service mechanics for Lexus, Toyota, Nissan, and Infiniti vehicles in the metro Atlanta area. We’ll diagnose your vehicle’s issues and get you back on the road in no time.

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