Oil use

[quesaisje]

Back again! My aging 2003 525i (211,000 miles) has been using oil, no leak apparent. I have added 5 quarts in the last 4 weeks, this after I took her in for an oil change, to the dealer. My independent mechanic suggested I switch from synthetic to regular oil. My next door neighbor, an Audi owner and a lot more knowledgeable than I am, says that wouldn't be a good idea. Your thoughts?