How to Fix Too Much Oil in Your Car

It’s a common scenario for car owners, especially those who prefer DIY maintenance: accidentally adding too much oil during an oil change. The immediate question that springs to mind is often filled with worry – have I damaged my engine? The good news is, in most cases, a little extra oil isn’t the engine-killer you might imagine. However, understanding the potential issues and knowing how to correct an overfilled oil situation is crucial for maintaining your vehicle’s health and performance.

Understanding the Risks of Overfilling Engine Oil

While a slight overfill might not cause immediate catastrophic damage, exceeding the recommended oil level can lead to several problems. The severity of these issues largely depends on how much excess oil is in your engine.

• Oil Aeration and Foaming: When the crankshaft spins at high speeds, especially with too much oil in the oil pan, it can churn the oil, introducing air bubbles and creating foam. This foamy oil is less effective at lubrication because air is compressible, unlike liquid oil. Effective lubrication is critical to prevent metal-on-metal contact and engine wear.
• Oil Burning and Increased Oil Consumption: Excess oil can be forced past seals and gaskets due to increased pressure. It can also splash onto hotter engine components, leading to oil burning. This results in increased oil consumption, potentially fouling spark plugs, and even damaging the catalytic converter over time. You might notice blueish smoke from your exhaust if oil burning becomes significant.
• Hydraulic Lock (in extreme cases): In very extreme overfilling situations, the oil level can rise so high that the pistons can’t complete their full range of motion. Oil is essentially incompressible. If the cylinders fill with too much oil, the piston’s upward movement can be restricted, potentially leading to a hydraulic lock. While less likely to cause immediate engine explosion, it can prevent the engine from starting or running properly.
• Increased Crankcase Pressure: Overfilling can increase pressure within the crankcase. This pressure can put stress on engine seals, potentially leading to leaks over time. It can also overwhelm the Positive Crankcase Ventilation (PCV) system, designed to remove blow-by gases from the crankcase. If the PCV system is overwhelmed, it can lead to oil being drawn into the intake manifold and combustion chamber, exacerbating oil burning issues.
• Reduced Horsepower and Fuel Efficiency: The crankshaft rotating through excess oil creates more resistance, known as windage. This increased drag can slightly reduce engine horsepower and fuel efficiency, although this effect is typically minimal unless the overfill is substantial.

Is a Slight Overfill Okay?

A minor overfill, perhaps a quarter or half a quart above the full mark on your dipstick, is generally not a cause for immediate alarm in most vehicles. Modern engines are designed with some tolerance. However, it’s still best practice to have the oil level correct. If you’ve only slightly overfilled, monitor your car for any unusual symptoms, such as smoke or leaks.

How to Identify Too Much Oil

The most reliable way to check for overfilled oil is by using your car’s dipstick.

1. Park your car on level ground and turn off the engine. Allow a few minutes for the oil to settle back into the oil pan.
2. Locate the dipstick, usually marked with a bright handle (often yellow or orange).
3. Pull out the dipstick and wipe it clean with a lint-free cloth or paper towel.
4. Reinsert the dipstick fully into its tube, ensuring it’s seated properly.
5. Pull the dipstick out again and check the oil level. The oil level should be between the minimum and maximum marks on the dipstick. If the oil level is significantly above the “full” or maximum mark, you have overfilled your engine oil.

Step-by-Step Guide to Remove Excess Oil

If you’ve confirmed that you have too much oil in your car, here’s how to safely remove the excess:

Using the Drain Plug Method

This is a straightforward but slightly messier method.

1. Prepare your tools and materials: You’ll need a wrench that fits your oil drain plug, an oil drain pan to collect the drained oil, and potentially a new drain plug washer (if recommended for your vehicle).
2. Locate the oil drain plug: This is typically found underneath your car, on the bottom of the oil pan. Consult your car’s repair manual if needed.
3. Position the drain pan: Place the drain pan directly beneath the drain plug.
4. Loosen the drain plug: Use your wrench to carefully loosen the drain plug. Do not remove it completely yet.
5. Gradually remove the drain plug: Unscrew the drain plug by hand, being ready for the oil to start draining. Control the flow by partially unscrewing the plug. Let a small amount of oil drain out.
6. Re-check the dipstick: After draining for a short period, tighten the drain plug back up to its initial tightness (not fully torqued yet). Wipe the dipstick clean and check the oil level again.
7. Repeat if necessary: If the oil level is still too high, repeat steps 4-6, draining a little more oil each time and re-checking the dipstick until the level is correct.
8. Tighten the drain plug to the correct torque: Once the oil level is correct, tighten the drain plug to the torque specification recommended in your car’s repair manual. Over-tightening can damage the oil pan. If you are unsure of the torque, tighten it snugly but not excessively. It’s always best to use a torque wrench. Replace the drain plug washer if necessary.
9. Dispose of the used oil properly: Take the drained oil to a recycling center or auto parts store that accepts used oil.

Using a Syringe or Oil Extractor

This method is cleaner and allows for more controlled removal of oil.

1. Purchase an oil extraction syringe or pump: These are readily available at auto parts stores or online. Look for one designed for oil extraction, often with a flexible tube.
2. Locate the dipstick tube: This is where you normally insert the dipstick to check the oil level.
3. Insert the extraction tube: Carefully insert the tube of the syringe or pump down the dipstick tube until it reaches the oil in the oil pan.
4. Extract the excess oil: Use the syringe or pump to draw out small amounts of oil at a time.
5. Check the dipstick frequently: After extracting a small amount of oil, check the dipstick to monitor the oil level. Repeat the extraction process and dipstick checks until the oil level is between the minimum and maximum marks.
6. Dispose of the extracted oil properly: As with the drain plug method, dispose of the used oil responsibly.

Prevention Tips

The best way to deal with too much oil is to prevent it in the first place.

• Know your car’s oil capacity: Check your owner’s manual or repair manual for the exact oil capacity for your engine.
• Measure accurately: When adding new oil, measure carefully using the markings on the oil bottles or a dedicated measuring container.
• Add oil gradually: Add oil in stages. Start by adding slightly less than the specified capacity.
• Check the dipstick regularly during refills: After adding a portion of the oil, check the dipstick to monitor the level and avoid overfilling. It’s better to add a little at a time and check, rather than pouring in too much at once.
• Level ground: Always ensure your car is parked on level ground when checking and changing the oil for accurate readings.

Conclusion

Overfilling your car’s engine oil, while not ideal, is usually a fixable issue. By understanding the potential problems and following the steps outlined above to remove the excess oil, you can ensure your engine operates smoothly and reliably. Remember, prevention is always better than cure, so take your time and measure accurately during oil changes to avoid overfilling in the future. Regular maintenance and attention to detail are key to keeping your car running in top condition.