Well, I may be out of line, but IMO any engine that burns up a quart in 200 miles is hardly a candidate for a synthetic switch! Sounds like time for a rebuild to me. What was the consumption of this engine with dino oil? What weight dino was used before, and what weight synthetic was used?
Note that I didn't make a blanket statement to just use any synthetic you feel like, I said exactly what brands & weights to use, which also happen to be what Mercedes-Benz specifies in writing for their engines. FWIW, Mercedes now *REQUIRES* the use of synthetics on all their engines, and the warranty is void if synthetic is not used. I can dig up some URL's with more info if you'd like...
Best regards,