Is Overfilling Engine Oil Dangerous?

While changing your oil every three months or 3,000 miles doesn’t apply anymore, we all know on some level how important it is to change our oil regularly. If you decide to skip your next trip to the shop in favor of some DIY automotive repair, do you know how much oil your engine requires? 

And no, the answer is not “fill it to the top.” 

How does engine oil work? Is overfilling engine oil dangerous? 

How Does Engine Oil Work?

Is changing your oil that important? The first step toward understanding its importance is understanding how engine oil works.  

Moderne engine oil acts as both a lubricant for the many moving parts in the engine and a heat transfer material. It absorbs heat from the engine’s interior and transfers it back to the oil pan, where it can dissipate. In some cars, air moving past the oil pan is enough to cool the oil before cycles back through the engine. In others, oil coolers act like miniatures radiators and work to cool the oil faster. These are generally only required in high-performance or heavy-duty operations. 

Problems With Too Much Engine Oil

Oil moves throughout the engine, but when filled to the correct level, the crankshaft doesn’t directly contact the oil. If you overfill the engine, the crankshaft moves so fast that it acts like the whisk attachment on a stand mixer, whipping the oil up into a frothy mess. This whipped oil is about as effective as dumping whipped cream into your crankcase and it creates an additional problem — pressure. 

As the oil foams up and fills with air, it increases the pressure in the crankcase and that pressure is always looking for an outlet. It will try to escape through the path of least resistance. That means blowing a hole through one of the many gaskets and seals in the engine, creating a leak. In the best-case scenario, you have a mess on your hands. In the worst, you’re looking at some expensive repairs. 

How to Fix The Problem

You’ll find many answers to the question of overfilling engine oil, from using a siphon to remove oil from the dipstick tube to releasing just a tiny amount of oil from the drain pan at a time. The easiest way to fix the problem before it creates more issues is to complete a new oil change when it comes down to it. Empty the crankcase by removing the drain plug in the oil pan. When that’s done, replace the drain plug and refill the engine with oil according to your manufacturer’s recommendations. 

Make sure you’re checking your owner’s manual. If you’re working on a DIY oil change, you’ll find that most oil is sold in quarts and most engines require between five and eight quarts of oil. Once you’ve put the necessary oil in, double-check the dipstick to ensure that you haven’t overfilled the engine. 

Don’t Overfill Your Engine.

More isn’t always better, especially when overfilling engine oil. Putting too much oil in your engine can reduce the effectiveness of your engine and can even result in leaks and expensive repairs. Check your owner’s manual to ensure you’re not overfilling your engine when you do your next oil change.