How long can I run my car with too much oil? Plus tips for an easy fix!

Changing the engine oil in your car is a necessary maintenance procedure that prolongs the life of an engine. Driving a car underfilled with engine oil can cause significant problems, but How long can I run my car with too much oil?

It is easy to overfill an engine if your vehicle’s required amount of oil is unknown or too much gets added. The unfortunate thing is depending on how overfilled driving could cause engine damage. 

But that’s not why you are here, so if you must drive your vehicle with an overfilled engine. Expect to get around a week or 1000 miles, whichever comes first, before issues will start to appear. Before we get into detail, you should understand the damage caused by driving with too much oil. So you can decide if the risk is worth taking.

Problems caused by driving with too much oil

A vehicle engine is a perfectly balanced machine built with many moving parts requiring a specific amount of lubrication.

Engine oil is that lubricant. When an engine is off, the oil sits in an oil pan at the bottom of the engine. As soon as the engine runs, the oil gets pumped around the engine. It passes through an oil filter to remove any debris which would cause damage. 

With an overfilled engine, the crankshaft rotates in the excess oil at the bottom of the engine. It wouldn’t be in direct contact with a large amount of oil if filled to the correct level, only enough to keep it lubricated. As the crankshaft spins, it churns the oil, aerating it. Aerated oil becomes a thick white solution, much thicker than oil is. Oil ways become blocked, and oil becomes ineffective at lubricating engine components. 

Another issue that can become apparent driving an overfilled engine is the rise in oil pressure. This extra pressure has no choice but to force the oil out of the engine through gaskets and seals. An expensive overhaul as the engine will need to be removed and stripped to repair.

The engine oil becomes like treacle in a vehicle driven overfilled for an extended period. It is challenging to drain, and that’s not the worst part. The engine will have irreversible damage to certain components.  

One last thing to note with an overfilled engine is once the oil is forced through the gasket and seals into other parts of the engine, a strong burning smell will not go away until the fault is rectified.

Can I drive my car with too much engine oil?

You can drive your car with too much engine oil, but it does need rectifying very quickly. An overfilled engine will usually start and drive as expected for the first few days. You may not notice any difference. There are, however, issues you should be aware of if you are driving your car with an overfilled engine which would mean your driving should be cut short. 

Pullover immediately if you notice the following when driving with excessive engine oil: 

• Suspicious noises from the engine
• Warning lights on the dashboard
• An excessive amount of smoke coming from the exhaust

Any above could indicate that you caught a severe issue just in time. But then again, it could be too late and prepare for a hefty bill. 

How long can I run my car with too much oil?

Driving for around a week with too much engine oil or about 1000 miles is possible. Every car is slightly different; unfortunately, 1000 miles in one car may be only 100 miles in another. 

The amount of overfill would also determine how far you could drive or if you should even attempt driving in the place. Significant engine component failure will become apparent very quickly if severely overfilled. Only drive if you do manage to overfill your engine in an emergency. It is much better to rectify the issue before starting your journey. The amount of money and time required to remove a bit of oil outweighs the cost of repair of total engine failure massively.

How much oil overfill is OK?

A small amount of extra engine oil is OK and will cause no damage to an engine. It is almost better to have too much oil than underfilled in terms of possible damage caused to the engine. 

An engine can be filled with around 10% extra oil and driven without any issues. A motor will burn some excess oil away, so there is no need to panic immediately. Remember, this is only relevant if inside 10% extra oil. 

How to remove excess engine oil

If you are confident in changing the oil yourself, the engine will need to be completely drained of oil and refilled with engine oil. If the engine oil filter was just changed and this is fixing an overfill, it won’t be necessary to replace the filter again. 

Remember to correctly dispose of excess engine oil at your local waste disposal facility. Engine oil is harmful to the environment, so it cannot be disposed of at home.  

A hand pump siphon will come in handy for draining excessive engine oil without needing to remove all the engine oil entirely. The added benefit of using a siphon is you control how much oil gets extracted. A siphon tube can be inserted directly into the dipstick tube, which goes into the engine oil pan. You can then pump, remove an amount of oil, and re-check the level. Repeat until at the maximum level on the dipstick.

If you are not confident doing this yourself, you will not take your vehicles to the garage to have a mechanic fix the overfill issue. Although, they may end up replacing the oil and filter all over again to ensure no further problems.

Will excess oil burn off?

A small amount of excess engine oil will burn off as the car’s driven. Some vehicles like diesel-fuelled cars burn more engine oil than petrol/gas engines. Excessive oil burning can be a sign of another issue like old engine oil and should be inspected by a mechanic if your car is burning through a lot of oil.

Can too much oil stop a car from starting?

An overfill of significant engine oil can stop the car from starting. When excess oil is forced into the engine cylinder, the oil fouls the spark plugs, which means the plug’s tip becomes coated in oil. Fouled spark plugs can no longer provide a spark to ignite the fuel due to the contamination meaning the car will struggle to start.

Final say

Overfilling an engine with excess oil can be done accidentally. It can be a costly mistake if it is not put right immediately. But to answer, how long can I run my car with too much oil? The answer is for about a week or 1000 miles if only just overfilled. But a short emergency journey should be the only distance considered if severely overloaded.