Oil getting into air filter

Has anybody had this problem before with oil getting in where the air filter is at? And what the problem might be? Thanks

What model, year and engine?

2000 Tacoma Pre-Runner v6

Is your air inlet in your wheel well? Is so, maybe you have driven over newly sealed asphalt or an oil spill and some got sucked in?

If you replace your air filter and clean the box, does the problem reoccur?