Skip to Content

Too Much Oil in a Toro Lawn Mower (This Can Happen)

You added engine oil to the crankcase and now you’re experiencing some issues with your mower. Could your problems be the result of overfilling your mower with oil?

Too much engine oil in a Toro lawn mower may cause engine damage due to overheating, seal damage, blown gaskets, or a hydrolocked engine.

Some problems can be easily fixed by correcting the engine oil level while others can be more significant and require an experienced small engine mechanic. I’ll go through them below.

Before troubleshooting your engine problem, remove the spark plug boot(s) and wait for the engine to cool.

Too much oil in a Toro mower

This post may include affiliate links. Purchases made through these links may provide a commission for us, at no extra cost to you. As an Amazon Associate, we earn from qualifying purchases.

Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

5 Effects of Too Much Engine Oil in a Toro Lawn Mower

1. Engine May Overheat

With too much oil in the Toro engine, the crankshaft and rod will have to push through excessive oil and not move freely.

This causes the crankcase pressure to increase and puts the internal engine parts under load.

The valve spring and rocker arm will get hot. The oil might not flow properly which can creates heat. This problem is further magnified by the aluminum that most engines are made with creating more heat.

The engine can get so hot it can pop out a valve guide or a valve seat from the engine block. If this happens to your engine you will need to have your engine scraped out by an experienced small engine mechanic.

2. Engine Seal Damage

Adding too much oil increases pressure in the crankcase. This pressure may blow out the seals and oil will drain out of the engine.

If you don’t identify blown seals quickly enough, you may end up with a blown engine due to running out of oil. This will cause a heat that is so hot that the engine can spin a rod or weld itself to the crankshaft.

This intense heat can also break the rod and send it out to the side of the engine block. The piston can weld itself to the cylinder causing it to seize.

3. Engine May Lock Up

Too much oil can find its way into the cylinder making the engine turn over very hard. If the oil gets past the rings, due to wear, it could lock up the engine. This is what is known as hydrolocked.

The combustion chamber, which should only have air and a small amount of fuel in it, now has oil in it.

When adding compression, the piston cannot compress the oil and it becomes hydrolocked. There is a good possibility the piston will bend when you go to start the engine.

4. Engine May Not Run Well and Smoke

You may experience the engine not running well with too much oil in the crankcase. Too much engine oil can get to the spark plug and foul out the plug.

Sometimes when there is too much oil in your engine it will run, but not very well. Too much engine oil can get up to the spark plug and foul out the plug.

The oil inhibits the spark that is needed to fire the fuel properly. It can cause your Toro mower to lose power and run rough.

Another reason your lawn mower may not run well is that oil can find its way into the valve train. This oil gets burned in the cylinder and you will find yourself in a thick cloud of whitish blue stinky smoke.

In addition to the smoke, when the air filter becomes clogged, the engine may pull air and oil out of the crankcase. Check out this article if you are experiencing smoke from your Toro mower.

5. Engine May Blow Gaskets

The engine problems you experience with a Toro push mower, riding mower, and zero-turn mower are mostly the same. The excessive heat from overfilling with oil may blow gaskets.

Replacing gaskets on a twin-cylinder engine is more expensive than repairs on a push mower engine because you will have to remove the engine from the lawn mower resulting in additional labor costs.

In Summary

Adding a little additional oil may not seem like a big deal, but it is actually a huge deal that can result in requiring a significant repair or an engine replacement.

So when doing oil changes or adding oil check twice and only add what is required by your engine manufacturer. Don’t assume a going over the required amount will be okay.

Don’t continue to run your Toro when you notice engine problems. Consult an experienced small engine technician when you experience engine problems that aren’t able to be fixed with a simple oil change or engine repair.

The technician can perform tests on the engine to determine if it is repairable or if it should be replaced.

How to Remove Excess Oil From a Toro Lawn Mower

If you overfilled your engine oil, you need to get the oil down to the correct level. The first thing you need to do is remove the spark plug wire for safety. There are several different ways to remove engine oil from your Toro mower.

  1. Drain Plug or Valve Port: You need to find the drain plug or valve port on the engine if your lawn mower has one. It may be found on the side of the engine by the dipstick or at the bottom of the oil pan under the lawn mower.

    Have your drain pan ready to collect the oil. Remove the plug for a quick second and replace it. Check your oil level.
  2. Oil Filter: If your engine uses an oil filter, you can drain a little oil by loosening or removing the oil filter to drain a little oil. Have a rag ready to collect the oil.
  3. Fill Hole: Your mower may not have a drain plug or oil filter. Many small engines on push mowers do not have a drain plug and you have to tip the mower over to drain a little oil out of the fill hole.
  4. Oil Extractor Pump: An oil evacuator works well to remove oil. An extractor will remove oil through a tube inserted into the engine oil fill hole.
  5. Turkey Baster: A turkey baster works well for removing small amounts of oil. Just make sure you don’t reuse it for cooking purposes after using it in your engine. These are pretty inexpensive to replace.

How to Not Overfill Oil in a Toro Lawn Mower

Before you change your lawn mower’s engine oil you need to look at your owner’s manual to find your engine oil capacity.

If you don’t have your owner’s manual, you can always use Google or the search engine of your choice to find the crankcase capacity.

Most small engines on push mowers will take about 3/4 of a quart of motor oil. A v-twin engine will usually take approximately 2 quarts.

A larger lawn mower commercial engine known as a big block can take 3 quarts of engine oil. These larger engines are known to be about 34 horsepower or larger.

The best way not to overfill your engine oil is to know your crankcase capacity and only add 1/2 quart of oil at a time. Keep checking the oil until you hit your mark.

If you are adding 1/2 quart at a time, when you get close to being full, just add a little bit at a time and check the oil level on your oil gauge or dipstick.

Will Too Much Oil Prevent a Toro Lawn Mower from Starting?

Too much engine oil can prevent your Toro engine from running. The oil pan on the small engines used on lawn mowers is very small.

There is not much room for error with such a small space. If you put too much oil in an engine your engine can hydrolock.

Hydrolocking is when oil gets up into the cylinder and past the piston. The oil then fills up the combustion chamber not allowing the piston to move to the top of the combustion chamber.

The piston is designed to compress air and not oil or water. When you pull on the rope or start the engine with a starter the oil will not compress and it won’t let the piston move. This is referred to as being hydrolocked.

Too much oil can also foul out the spark plug and not allow the engine to run. Another damage too much oil can do to an engine is oil getting into the carburetor through the valve train causing the engine not to run.

This oil can pass through the carburetor and into the air filter which will also cause your engine not to run.

Still Having Problems with Your Toro Lawn Mower?

It would be great to own a problem-free lawn mower, but it’s never the case. No matter what brand mower you own, you’re going to run into problems the longer you own it.

To help you troubleshoot your mower problems, I have put together a list of common problems along with causes and solutions to fix them. Check out Common Toro Lawn Mower Problems and Solutions to learn more.