A6 Oil in exhaust

I have a 2001 A6 and smoke started billowing out of the tail pipes. This has happened before and I was told a oil tube froze and oil was sent in the
turbo and exhaust. Does anyone know what this tube is and can this be avoided. It has happened twice to me now in two years.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.