Perhaps a dumb question but what temperature rating should the brake fluid meet for a venture? (1999)? My Haynes states only that it meet Dot 3. I am sure my resevoir says Dot 3 or Dot 4. My local parts store sells 3 different boiling point DOT 3 fluids, 550F, 478 F and someting else. The 550 states that it is for Fords but that may be just because FORDs need that temperature. My other vehicle is a Ford and I have about 3 full bottles of the 550 that I intend to use in either vehicle (to avoid having too many open top up bottles). Is there any harm in using a higher temperaure rating?

Just use the rest of what you have on hand. Provided that it isn't old and has been kept in a tightly sealed original container.