After I run my dixion mower with a 15 hp briggs on it after we mow for a while I notice there is oil in the air filter area. And after a few hours of mowing the filter is ruined with oil in it. Any ideas what to check. This thing starts and runs great and there is no smoke or rattles when you start it at all... do I have a valve problem? Thanks for your help

Check your oil level and see if its over full.
Do you have any oil leaks

Leaks no oil and is right on the full mark.. with clean oil. It seems to be coming from vent tube or breather tube?

The block breather could be bad
Does your dipstick fit tight at the top.

Classic symptom. Replace the breather.

I will check it today thanks much

I did relplace it and after 30 min of mowing doing the same thing.. oil in the filter and carb. This thing doesn't smoke or any thing.. any thing else to check? Thanks.

I experienced the same problem with my V16. Check that the end of the rubber oil breather tube is pointing over the carburetor air intake. Any oil coming out of the breather tube will go back into the engine and be burned off, and so the oil will not be able to splatter around the inside of the air filter.