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Why a Zero Turn Lawn Mower Begins Smoking After an Oil Change

You follow your manufacturer’s recommendation and regularly change your engine oil to keep your zero-turn running at its best.

You thought you were doing a good thing, however after you changed your oil, the mower started to smoke. You try to retrace your oil change steps to try to determine what may have gone wrong.

A zero-turn lawn mower begins smoking after an oil change when the engine oil level is too high or too low; the viscosity and type of oil are incorrect, or oil was spilled onto a hot engine or muffler.

Take all safety precautions as outlined in your operator’s manual to avoid injury. Be careful working around a hot engine.

Pouring engine oil

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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.

This is Why Your Zero Turn Starts Smoking After an Oil Change

Spilled Oil

Oil can drip onto the engine or muffler when you change the oil in your zero-turn lawn mower. This will not hurt your mower. The oil will burn off the engine or muffler once it becomes hot.

When it does, it begins to smoke. To prevent this, be sure to wipe any oil drips from your mower after refilling the engine oil.

Too Much Oil in the Engine Crankcase

You may have overfilled the crankcase when you added fresh engine oil. Too much oil will cause pressure to build in the crankcase.

This pressure can push oil into the cylinder through the valve train. When the oil burns off in the cylinder a bluish-white smoke is emitted from the zero-turn.

This thick smoke can also plug the air filter causing the engine to run sluggish because it isn’t able to get air. When this happens, replace a plugged filter plugged with smoke and oil.

Also, check the spark plugs. Replace the plugs if you find them covered in oil. Check and correct the engine oil level. Remove the dipstick and wipe it off with a clean rag so you can get a good oil level reading.

Reinsert the dipstick into the oil and remove. Read the level on the dipstick. A good level is when the oil registers between the full lines.

When you find too much oil, remove a little oil from your zero-turn. There are several ways to do this:

  • Remove the drain plug and quickly replace only allowing a little oil to flow into the oil pan.
  • Remove the air filter and allow a little oil to drain out of the filter.
  • Use an oil evacuator to remove a little oil out of the oil fill area.
  • Use a turkey baster to remove a little oil out of the oil fill area. Yes, this is like a baster you use when cooking a turkey. If you take the one out of the kitchen, don’t use it for cooking purposes. You’ll need to purchase a new baster.

Once you have removed some oil, recheck the oil level on the dipstick. Remove or add a little oil until the level registers within the full lines on the dipstick.

Not Enough Oil in the Engine Crankcase

Just like having too much oil in your crankcase can cause smoking problems, too little oil can also cause the engine to begin smoking. Oil is needed to lubricate moving parts in the engine. Without it, friction will build causing extreme heat.

Your zero turn starts smoking when the heat buildup is so excessive the oil begins burning off and the engine components begin to melt. If you find your crankcase engine oil level is low, you can attempt to add fresh oil to correct the problem.

Understand, if your engine begins smoking because you don’t have enough oil in the crankcase, it is highly likely engine damage occurred as a result of the extreme heat. I recommend taking your zero-turn to an experienced small engine mechanic to be diagnosed.

Wrong Engine Oil

The grade of engine oil is important to keep the engine properly lubricated. When using the wrong viscosity of oil, it can begin to burn and emit smoke. Always use the viscosity of oil recommended by the engine manufacturer.

Use air-cooled engine oil to help keep your engine cool. This is an oil that contains a high concentration of zinc that acts as a cooling agent. Regular engine oil, like the oil used in vehicles, doesn’t include much zinc because engines are cooled with liquid.

The ambient temperature while you are operating your mower can also affect the oil viscosity you must use. Most lawn mower manufacturers recommend using SAE30 or 10W-30 engine oil, but you may have to change your oil viscosity to 20W-50 when operating in higher temperatures.

Check out this chart provided by Kawasaki Motors that reflects the oil viscosity in relation to temperatures.

kawasaki air cooled engine oil chart
Kawasaki Engine Oil Viscosity & Temperature Chart

Other Reasons a Zero Turn Begins Smoking

You may think your zero-turn lawn mower is smoking due to an oil change, but it may be a problem that was already developing in the engine.

A zero-turn can smoke when there is an engine gasket failure causing an oil leak onto a hot component. The engine may also develop a piston ring or valve train issue. Read more about these internal engine problems here.

Still Experience Problems with Your Zero Turn Mower?

Many different types of problems can develop in a mower. It doesn’t matter what brand you own.

While some mowers are built with stronger materials, bigger filters, better engines, and tougher spindle housings, they are all going to break down and cause issues at some time. Some may just not develop problems as quickly as others.

I put together a guide with common things that go wrong on zero-turns. In this guide, you will find a list of causes and solutions for a mower dying, smoking, vibrating, not starting, having cutting issues, and more.

Check out my guide at Common Zero Turn Mower Problems: How to Fix Them

If you still can’t find the solution to your problem or you don’t feel comfortable troubleshooting or repairing your mower, it is best to have an experienced mechanic check out your mower.

You can visit your local dealership that provides repair support for your brand mower. You may also find a lawn mower repair shop with experienced small engine mechanics.