How important are the vital fluid replacements for a car? I have a 2013 RDX but I guess in this case, the question would apply to any car. It's not like I would never do it, but I feel like they ask about it every time I go into service. I ask because I went in for an oil change at an Acura dealer and they wanted to tack on another $250 for brake fluid replacement as well as a rear differential fluid replacement. My car has around 45000 on it.

 

if you check out the owners manual; it will state something like; OEM brake fluid is rated for 3 years, change. then change yearly after that.
and I believe the differential fluid will have a code that pops up on your MID..telling you to change the differential fluid..
coolant is good for 5 years, I think...