Brake fluids are notorious. When I started in this industry, DOT 3 brake fluids were used everywhere, but they had a terrible reputation for damaging paint. For custom guys that was the kiss of death. Just the mention of bleeding brakes would raise eyebrows and cause skin to crawl.
Then suddenly we were saved. Somebody developed DOT 5 a silicon based brake fluid. You could pour it over your new custom paint job without a problem. We thought we were saved.
Then it started to get confusing. Another chemical engineer developed DOT 4 supposedly for high temp applications. What the hell?
Suddenly I didn’t know what to use where. Of course most manufacturers put their recommended fluid on the caps of all master cylinders, but that doesn’t work for some custom applications.