As a Service Manager at an auto shop, a member of the profession or "mere trade", it is about time to weigh in here. Dukeofmuffins, spend the $25 for the lab tests. Once you have conclusive proof, approach the service manager as politely and succinctly as your posts have been. Remember, facts talk and B.S. walks. I will assume at this stage there is no "corporate conspiracy" to rip you off, but a lazy/dishonest employee who got paid for doing a job they did not do. As a service manager, I would want to know. The lab report stops a "he said/she said" argument with actual fact. It would also give the manager the leverage to ask for said employee's resignation (in today's society firing somebody can be legally difficult). If it were the shop I am at, with that lab report in your hand, I would reimburse you the $25, redo the flush with you watching if you desired, and throw in a couple of free oil changes for your trouble along with a big apology and a thank-you for ratting out a bad employee. If there is a "corporate conspiracy" to rip you off (ie: they stonewall), it is worth the $25 to know that this business establishment should be avoided at all costs. As for drain and fill, the idea is to have clean fluid, not semi-clean fluid. 4-5 drain and fills will use a minimum of 8-10 quarts of fluid, probably more, and should include a new filter EACH time, and you would still have fluid that is not 100% clean. Total your costs for that versus my shop's $129.95 flush where fluid and filter are extra. Probably less than what you spent, you get 100% clean fluid, and a receipt to show GM if your trans needs a warranty rebuild. If they did put in an additive that turned your fluid grey (and I know of no additive that would) you should have the right to have them remove the unauthorized additive with a free flush. My feeling is that you should find a good independent shop that pays their employees a decent hourly wage, no commission or flat rate. The flat rate system encourages techs to take shortcuts to earn a living wage and a commission on parts and service work lets lazy employees steal from customers ...but that is another rant. Good luck and keep us updated.