For the brake work I'm about to do on my 1994 Jag XJS I'm looking at the fluid. Dot 4 is required and I've read on the Jag forum that the highest boil point you can get is recommended. It's a very heavy car with a good pulling engine. I got Break Best dot 4 with a 475 degree boiling point since it was the only dot 4 at the O'reilly I like to shop at. I can get Valvoline synthetic dot 3/4 at Advance down the road with a 480 boiling point. I can get Amsoil online for a lot more than either of these but it has a 580 degree boiling point. So, is there much difference in the real world between any of these? Is the amsoil really worth double (and for a smaller bottle)? Is there another brand I should look for?