Holy crap, if you really own a shop and this is the way you do business I can see why your customers keep coming back. It do to the fact you sell them on half assed service. If indeed you do own a shop, you give reputable shops a bad name and are probably one of those that sell unkkowing people lots of extra parts that they don't necessarily need. Let me take a guess, do you own a Midas Store?!
Like everyone else has stated, simply draining the fluid out of the reservoir and refilling it has nothing to do with the fluid in the lines. If you have EVER bled the brakes you'll notice that when you do so the fluid always goes from dark (used) to lighter when the new fluid eventually reaches the caliper. And I will take your bet that my fluid is cleaner than yours. When can you come to my garage and we'll take turns bleeding each others fluids?
Get a frickin clue man and stop selling people a bunch of crap.
Rick
