Can you put regular unleaded gasoline in a 2000 C230 Mercedes Benz?

Yes, I have been filling my 1997 Mercedes C230 with regular unleaded for years and NO problems or loss of power. If the engine knocks, that means the octane rating is too low, but if it does not, the octane is fine. Mine never knocks and runs fine on unleaded regular. Why wear a size 13 shoe if you only need size 12?