If your lawn mower suddenly developed a problem with oil leaking out of the exhaust, it could be a simple fix or a more complex one.
The simple fix could be that you simply overfilled it with oil. Check the oil level and see if that is the case. If the oil level is too full, drain some oil and check it again.
If the oil level is fine, then a component has failed in the engine. A series of tests will need to be completed to determine what the problem is. Many people do not have the tools to accomplish these invasive tests so it would be recommended that a lawn mower engine repair specialist perform them.
You can check our Locations page to see if there is a lawn mower shop near you.
If your lawn mower leaks oil out of the exhaust, it would be recommended that you do not use it until the problem has been corrected. Raw gasoline could be leaking out of the exhaust as well and it could potentially catch fire. This fire could total your lawn mower and catch other things on fire as well.