oil on undercarraige how can i clean it
 

Just got major oil leaks fixed on my 05 a6 4.2L thought it was still leaking so took it back to my shop. mechanic told me the undercairrage has absorbent pad in it which is soaked with oil. that is what the oil is leaking from and cant be rinsed off due to the absorbent pad. how true is this?