A service adviser at a local garage claims that the brake fluid must be changed every 2 years here in North Carolina because of high humidity. Never heard of this. A ripoff?
Personally, I think that a 3 year change interval is more realistic–as well as less costly–but he is correct that brake fluid does need to be changed periodically.
Its hygroscopic nature causes brake fluid to absorb moisture from the air, and over time, this does dilute the brake fluid. The result of brake fluid dilution is rusting and corrosion of brake caliper pistons and brake lines over time, with the possibility of brake failure.
Additionally, it is possible to temporarily lose all braking ability on a long down grade if the brakes are “over-used”, because the water in the brake fluid will actually boil as a result of the overheating of the brakes.
So, he is correct in general, but I think that he is a little overzealous concerning the schedule for this procedure.
If your mystery vehicle is one of the Japanese makes, it is very possible that the mfr’s maintenance schedule calls for brake fluid replacement every 3 years/36k miles.