What does it mean when your lawn mower blows white smoke?

Answered by Randy McIntyre

When your lawn mower blows white smoke, it is usually an indication of burning oil. This can be a cause for concern, as it may indicate an issue with your engine. There are several possible reasons for this, and I will explain them in detail below.

1. Overfilling the crankcase with oil: One common cause of white smoke is when the crankcase is overfilled with oil. This can happen if you accidentally add too much oil during an oil change or if there is a problem with the oil level sensor. When the crankcase is overfilled, the excess oil can get into the combustion chamber and burn, resulting in white smoke. It is important to ensure that you are adding the correct amount of oil specified for your lawn mower.

2. Incorrect oil grades: Another possible cause of white smoke is using the wrong oil grade for your lawn mower. Different engines require different oil grades, and using the wrong one can cause issues. If the oil is too thin, it may burn more easily and result in white smoke. On the other hand, if the oil is too thick, it may not lubricate the engine properly, leading to excessive friction and potentially causing the engine to overheat.

3. Operating engine at a greater than 15-degree angle: Lawn mowers are designed to operate on level ground, and tilting them at an angle greater than 15 degrees can cause oil to flow into the combustion chamber, leading to white smoke. This can happen if you tip the mower to clean the underside or if you mow on uneven terrain. It is important to always operate your lawn mower on level ground to avoid this issue.

4. Other potential causes: While burning oil is the most common reason for white smoke, there are a few other possible causes to consider. For example, a blown head gasket can also result in white smoke as coolant enters the combustion chamber and is burned along with the fuel. Additionally, a damaged piston ring or valve seal can allow oil to leak into the combustion chamber, causing white smoke.

If your lawn mower is blowing white smoke, it is likely due to burning oil. This can be caused by overfilling the crankcase, using incorrect oil grades, or operating the engine at a greater than 15-degree angle. It is important to address this issue promptly to prevent further damage to your engine. If the problem persists or you are unsure about how to resolve it, it is recommended to consult a professional or take your lawn mower to a qualified service technician.