too much oil in lawn mower

What to do If There is Too Much Oil in The Lawn Mower

If you use a gas powered lawn mower then oil is an essential part of the running and maintenance of your tool. It helps to lubricate the moving parts and stops the engine from overheating. However, many of us have been in the sticky situation of having added too much oil to the lawn mower.

But don’t panic, provided that you deal with the lawn mower oil overfill, this shouldn’t cause too many problems. It’s when you carry on and run the mower regardless that you may have issues down the line.

Here’s our guide on what to do if there is too much oil in the lawn mower.

You likely paid a decent amount of money for your gas powered lawn mower so the last thing you want is for it to become damaged. Repairs can be costly and even if you can do them yourself, they’re still time consuming. What’s more, in some cases, you may find that the damage is irreparable and the entire mower needs replacing which can again, mean putting a dent in your bank account.

1. Engine May Overheat

One of the most common issues associated with too much oil in a lawn mower is that the engine can overheat. This happens because the rod and crankshaft need to force their way through more oil and they are not as easily able to rotate. As a result of this, the pressure from the crankshaft becomes much higher and this increases the load on other working parts of the mower engine.

Since the oil is not able to properly flow, the first things to heat up will be the rocker arm and valve spring. Almost all mower engines are made from aluminum and this is a material that gets incredibly hot. When this happens to your mower engine, it can result in valves of valve seals popping out of the engine block. In this situation, it will be necessary to have the engine scraped out.

2. Damage to the Engine Seal

Another problem that might be caused from a lawn mower oil overfill is damage to the seals within the engine. You might not think that this sounds like too much of a problem but that is not the reality of the situation.

Oil could blow out of those damaged seals, lowering the amount within the engine. Sounds good, right? After all, you did have too much oil in there. But this can lead to the opposite problem; all of the oil blowing out, leaving the engine with none. When this happens, the engine will heat up and quite often, you’ll end up with a spin rod that’s welded to the crankshaft.

Another issue that can happen as a result of this is that the excess heat might break the rod which can then come out of the engine block. Inside the cylinder, it is possible for the piston to become welded and everything will simply seize up.

3. May Lock up the Engine

If you add too much oil to your lawn mower then it is possible for the excess to get into the cylinder. What happens because of this is that the engine will be forced to turn over much harder and if any oil gets behind the rings, this may cause the engine to lock up. Do keep in mind that this typically only happens if the rings have worn over time. When this happens, it is known as hydrolocking. You want to avoid this if you want your mowers engine to last a long time.

Essentially this means that the combustion chamber gets filled with oil. For the mower to function correctly, this chamber should only ever have fuel and air inside. As a result, the piston finds it almost impossible to compress the oil so it locks. It is possible to bend the piston to get the engine going but it’s just better to avoid putting too much oil in the mower in the first place.

4. Blow Your Gaskets

If you have a twin cylinder engine, then the issues with overfilling with oil will be largely the same. Excess heat can cause gaskets to blow and this can be a very expensive problem to fix. Compared to the cost of repairs on a push mower, things will be far more pricier and let’s not forget that it isn’t only the parts you’ll have to fork out for but labor costs too.

Some people are tempted to add a little extra oil for good measure and this doesn’t seem like much of an issue. However, too much too often could result in very serious problems like this which might then require something as expensive as a full engine replacement. It’s just not worth the risk.

How to Remove Excess Oil From a Lawn Mower

From time to time, we all make mistakes and I’m pretty sure that every gardener will have put a little too much oil in the lawn mower at one point or another. If this has happened to you, don’t start panicking, it is possible to remove the oil and avoid the problems we have looked at above.

Even better news is that there are a few different things you can do to get that excess oil out of your mower.

changing lawn mower oil

Even better news is that there are a few different things you can do to get that excess oil out of your mower. 

  • If your lawn mower has a drain plug or valve port then locate this; usually it will be found on the side of the engine and in most cases, it’ll be near the dipstick or near the bottom of the oil pain. Make sure that the pan is in place to catch the excess oil before you remove the plug. You’ll only need to remove the plug for a second to release the oil. Then you can check the oil level again and remove any more if it is needed.
  • Some lawn mowers have an oil filter and you can use this to drain a small amount of oil. All you need to do is loosen the filter or remove it entirely and the oil can be drained. Just make sure that you have something to collect what comes out; an old cloth should be more than sufficient. 
  • Some lawn mowers do not have an oil filter or a drain plug but that doesn’t mean you can’t remove oil if you’ve added too much. You can simply take the oil out via the same route it went in; through the fill hole. You’ll need to tilt the mower to allow the oil to flow out; when you’re done, be sure to check the level again before using the mower.
  • You can use something like an oil extractor pump which is effective in taking out excess oil using a tube which you place into the fill hole of the mower.
  • If you cannot do any of the previous methods then you might be able to use something as simple as a turkey baster. This is a good option if you’ve only added a very small amount of excess oil

How Much Oil is Needed in a Lawn Mower?

According to Briggs and Stratton, lawn mower oil should be changed every 50 hours of use or once a year, whichever happens first. For a walk behind lawn mower, the capacity of the oil tank is usually between 15oz and 18oz. However, this will vary by model so it’s important to check your user manual which will tell you how much oil you’ll need to put in. 

If you are using a riding mower, then naturally the oil capacity will be much higher. Generally speaking, this could be anywhere between 48oz and 64oz. Again, your manufacturer will tell you the right amount of oil for your model. It’s also worth noting that, with a riding mower, you will only need to change the oil for every 100 hours of use as opposed to every 50 hours. 

lawn mower oil change

How to Avoid Overfilling the Oil in a Lawn Mower

One of the main responsibilities of owning a gas powered lawn mower is maintenance. A part of this is regularly checking the oil levels of your lawn mower; if there isn’t enough then the engine won’t be correctly lubricated but you also want to make sure that you don’t overfill the oil reserve. Use the mower’s dipstick to check the oil level and there will be markings on this to help you make sure you put the right amount in.

The best way to avoid overfilling your lawn mower is to familiarize yourself with the machine. When you purchase the tool, avoid the temptation to just get on and use it; spend some time reading through the user guide as this will provide you with details on how much oil to use as well as many other important things. Remember that no two models are the same so even if you’re used petrol mowers for years, your new tool may be slightly different to what you’re used to.

If you don’t have the user manual or misplace it, the manufacturer’s website can be a useful place. Moreover, all manufacturers have some way of contacting them so either pick up the phone, join a live chat or send an email before filling the mower up with oil.

When checking the engine oil, it’s important to point out that you should do so when the engine is cool. If you do it when it’s still hot, some oil may still remain in the crankshaft so you won’t get an accurate reading. This can make it look as though there’s not enough oil so you’ll refill it but when everything settles, you’re left with too much.

Watch this video on how to change lawn mower oil


Overfilling your lawn mower with oil can cause a variety of problems. Things like engine overheating, locking and blowing gaskets can all become an issue. However, by regularly checking the oil level and reading your user manual, you should be able to put just the right amount in. 

We all make mistakes, so if you have accidentally overfilled your lawn mower with oil then there are fortunately several ways you can take this back out again.

Further Reading

Andrew Fisher

Andrew Fisher

Andrew is a dedicated father of three who really takes pride in his lawn and garden. You'll find Andrew behind the scenes of almost everything Edge Your Lawn produces. When he's not helping readers find all the information they need, he's in his backyard working on his lawn and garden landscaping. This year he hopes to build an outdoor deck and sort out his veg patches.

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