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If you put too much oil in your car, nothing will happen until you start it, and nothing catastrophic will happen immediately afterwards.
Oil circulates when the crankshaft rotates. Excess oil whips and churns during this process because it can’t flow. That foamy oil doesn’t lubricate well and can lead to increased pressure in the crankcase (which can cause oil to leak past seals and gaskets).
These issues will not cause your engine to explode and die, but you might need a mechanic to drain the excess oil before driving.
Have you overfilled yet?
If you’re reading this before topping up your oil to balance the risks, remember that the ideal time to take an accurate oil reading is when the oil is warm enough to flow easily but not immediately after driving when the engine is extremely hot.
Don’t top up your oil based on a cold or hot reading. After driving for twenty minutes, let your car sit for ten minutes to reach a reasonable temperature.
Editor’s note: If your car is using too much oil, a top-up will only refill what’s lost from a possible leak or excessive combustion cycle. A mechanic needs to diagnose your oil consumption issue for a proper fix.
If you’ve already overfilled your car
Overfilling with oil isn’t a massive cause for concern unless you have overfilled it significantly and need to drive it now.
When the oil level is well above the maximum mark on your dipstick, issues with oil aeration and increased crankcase pressure can occur.
You might notice symptoms like blue exhaust smoke or oil leaking through the engine as excess oil gets forced past seals and gaskets.
The main thing to remember is that occasional oil top-ups are routine maintenance, and going slightly over the full mark isn't close to being a problem.
If you've added so much oil that the dipstick is caked, have a mechanic drain it to the proper level before doing any significant mileage.
What’s the danger?
Piling on the miles with a significantly overfilled engine will force oil out of the seals and gaskets that create a sealed unit. After parking, you will leave small pools of oil behind and produce more smoke from your exhaust.
Of course, these aren’t dangerous symptoms – what is harmful is when that frothy oil attempts to lubricate components with tight heat tolerances.
Poor lubrication means excessive heat, which increases wear and tear. Your engine's critical components – like bearings, camshafts, and pistons – rely on a precise film of oil to prevent metal-to-metal contact.
When the oil becomes frothy and loses its lubricating properties, these components grind against each other, generating extreme heat and causing potentially catastrophic wear.
Complete engine failure is one possible outcome, although if that were to occur, it would probably be from the frothy oil exacerbating an existing problem.
This is in contrast to filling up with the wrong fuel – drive with that in your tank, and you could cause irreversible damage immediately.
What to do about it
Take your car to a mechanic - the local one down the street can handle this easily. They'll drain the excess oil quickly and correctly without any fuss.
It's a simple job that doesn't require special skills or expensive equipment. Most garages can do this in less than an hour at a minimal cost.
If you're nearing your regular oil change, consider getting a full service (minor or major to suit your interval).
Don't try to drain the oil unless you are a mechanic with suitable equipment. One wrong move could cause more problems than you started with.
Professional mechanics do this daily and know how to handle it safely. Plus, you can ask them to check your car for any other issues.
For instance, we'll let you know if we notice anything that needs attention while servicing your car, such as issues with tyre tread depth. We provide correct information to help you decide if and when you want to address the problem.
Find out more
Call 01694 722626 or message us for more information about oil problems. Advice is free, and if you’re local, you can pop down to see us.