I recommend not using silicone-based (DOT 5) fluid. Its lack of hygroscopicity (i.e., it does not absorb water) sounds like a good thing, but in fact it's not. Moisture will get into the brake hydraulic system with normal usage and changes in ambient temperature and humidity. That's a given. Ordinary brake fluid is designed to absorb and assimilate a fair amount of moisture without causing substantial corrosion problems. With silicone fluid, the water will accumulate in slugs at the lowest points of the system...and stay there, where it will aggressively corrode whatever it's touching. Practically speaking, if there's more than a really small slug's worth of water in your system, it's faulty and/or neglected, but the fact remains, this slugging rather than absorption of water is just a change, not an improvement. It only takes a very small amount of concentrated water sitting in one place in a steel line to initiate dangerous rust-through. And remember, it doesn't matter if the brake fluid has a sky-high boiling point; if there's even a small slug of water in the system, it's still going to boil at 212°F, and turn into steam, making your brake pedal soft and squishy or worse. Furthermore, it is very difficult to get all the air out of silicone brake fluid that is introduced with just normal handling and pouring, so it is very difficult to get a good, firm pedal.
There is an enormous range of conventional non-silicone brake fluids on the market. You can get whatever properties you want (e.g., high boiling point) without having to go to a silicone-based fluid.
And as if that weren't enough, the cost and effort difference between regular and silicone fluid is such that you can flush the system with conventional fluid every few years for a long time before you equal the cost of just one silicone fluid changeover.
Shop carefully. All silicone fluid is "DOT 5". The highest spec category for non-silicone fluids is "DOT 5.1".
DOT 3 (original fill after '69, replaced the old J1703 fluid spec), DOT 4, and DOT 5.1 fluids are all intermixable.
DOT 5 (silicone fluid) cannot be mixed with DOT 3, 4, or 5.1.
We can get much higher performance brake fluid now than was available when our cars were new. I haven't looked around for brake fluid performance comparison tests — I imagine somebody's done them — but not long ago when I was shopping for half a litre of brake juice, I was faced with at least four choices of Prestone DOT 3 fluid. I don't recall all the varietal names, but there was one that said "for Ford vehicles", one that said "for ABS brake systems", one that was just plain, and...at least one other. All DOT 3, 4, and 5.1 fluids are intermixable, so there's no danger of a situation like "ohmygawd, I put Ford fluid in my Dodge/I put non-Ford fluid in my Ford".
Each of these multiple types of Prestone DOT 3 fluid had different boiling points, though there were two boiling points listed on each bottle; one denoting the minimum required for the DOT 3 category, and the other indicating the characteristic of that particular fluid…read carefully; the labelling isn't very clear. It's even more confusing than that; some fluids list both a dry and a wet boiling point, and some DOT 3 fluids have a higher (better) boiling point than some DOT 4 fluids.
Really, it should not be necessary to spend money on exotic brake fluids. Use a good brand of DOT 3 or DOT 4. Shop carefully, use a reputable brand, and be choosy. I have tended to use Castrol LMA DOT 4 when I can find it. Flush the system every few years and you'll be in fine shape for a long time to come.
