Did I miss something? I never changed the trans fluid in my '(97 ) C280, 100K miles and the trans worked fine. Think of it. Most trans changes only remove about 25 to 39% of the initial OE fluid. Trans are closed systems, so what happens to the synthetic fluid (other than a possible leak) that would require a fluid change? Oh, I also own a 30 year old Chevy Blazer. Never ( yet) changed the fluid. Have added, but the old Powerglide really works well. OK I must be a nut, right.