Of course prices at your dealership were similar, they are inflated. You can get valvoline for way less at any auto parts store
wet boiling point is NOT wet boiling point is NOT wet boiling poit. different fluids, still rated for dot4, can have different boiling points. Also different fluid can have different affinities for absorbing water.
And wet boiling point doesn't mean anything since you shouldn't be letting your fluid get wet. That is also the reason to NOT use race fluid on the street since it is less likely to get flushed often and more likely to see water from rain.
Not to mention with the price of race fluid vs something like valvoline you'll be more willing to do a flush that costs you about $3 vs $15 on a more frequent basis
If it meets dot 4 standards it meets dot 4 standards. Brake fluid (dot 5 is the expection) absorbs water. All glycol based fluids will do this. Do not put slicone brake fluid in your bike. DOT 5.1 is ok to use. DOT 5 is not. Yeah don't get water in it but it will absorb water with time.
Has anyone on here ever had there brakes fail?? I'm guessing no. Unless you on the track it really doesn't matter imho. Even then unless you are one serious mofo i don't think you going to over heat your brakes. Now yes some products exceed dot 4 standard. Are they better? Not really unless you overheating your brakes.
however two different "dot 4" fluids can still have different wet and dry boiling points since they can exceed dot 4 by different amounts.
and yes they all absorb water but they don't all absorb it equally. race fluids with very high dry boiling points typically absorb water easier than lower bp fluids.
and since you are right that it will absorb water over time is why it is important to change it often and most street riders are more likely to do that if the fluid isn't $15/qt like motul can be at their local store.
by way of example, I'm staring at a bottle of Prestone DOT 4. Wet boiling point 311F (dry not listed). I have an old (unopened) bottle of valvoline synpower dot 4 rated at 330f (480F dry) Interestingly their web sight lists their fluid at 500F dry but isn't showing the wet temp. I'll have to check a bottle at the store. but frankly that is pretty damn good for the price the fluid is. I just checked castrol gtlma and they are claiming 509F and
But both are Dot 3 and DOT 4 rated and yet have different wet points. In fact Motul RBF600 is only a Dot 4 fluid yet of course is rated at 600f dry and 421 wet. not sure what part of the DOT spec keeps it at DOT4 but that goes to my point: just because it is dot for doesn't mean it has the same wet boiling point as other dot 4.
once a year is likely fine. I would also say just save yourself some money and use a cheaper dot 4 come spring time.
another thing to consider, that might not pop right out from what me and 600f3rider are saying: the wet boiling point is a spec number. it is not absolute. that is to say, if you get more water in your fluid than what they allow for spec testing, then your boiling temp will be even lower. So instead of the 500F dry boiling point you could be looking at a 250f boiling point; well below even the dot 4 minimum of 311f
also if you ever experience a mushy pedal from boiling fluid, flush it. even if it was just from getting REALLY hot and not cause there was water in it ... cause there is more water in it now. everytime it boils it absorbs water even faster than normal.
Wow. I thought Valvoline had a higher dry bp. Anything under $15 is cheap. Race quality brake fluid is $60+/qt. Castrol SRF comes to mind and that's close to $80/qt with a racer's discount. I use ATE Superblue because it's rated at 536 dry bp and you can get it for ~$12/qt. I bought a case when I was tracking my M3 and now using it for my bike. Most people that bleed once a year or more won't have to worry about wet boiling points.
Once a year is a good interval for bleeding brakes. More if you go on very spirited rides often. You don't have to be a fast mofo to boil your brakes. If you're on the brakes for a long time like going downhill and you drag your brakes or if you just have bad braking technique, it will boil. The friction of the pads on the rotor will heat up and transfer to the fluid.
Mushy brake feel isn't caused by water in the fluid, it's air in the system. Air compresses more than fluid so your brake lever travels more to get the same braking if you have air in your system.
True about water itself not making brakes feel mushy, but more to the point discussed here water in the fluid can allow it to boil easier and boiling fluid causes [drum roll please] bubbles in your fluid which makes a mushy brake during operation.
500f (new valvlone) is pretty damn good for store fluid going in daily drivers. so was the older ones 480f. really not that bad at all.
Yeah, if you don't ride on the track you don't need the better stuff. I'm not even convinced people who ride on the track need the "better" stuff. Motorcycle have been turning wicked fast lap times well before dot 5.1 and that 600 stuff. I have never experienced fad at the track i'm probably low intermedate level nesba scale wise which would make me intermediate everywhere else.:lol
I have used Valvoline for a while in my street and track bikes, (cars too) and love it. It is cheap, available everywhere, and performs well. I can't see spending big $$ on brake fluid that performs better on paper if you aren't going to ever be able to tell the difference in reality (especially on the street). If you change it regularly and often, Valvoline (or probably any DOT4) will be more than fine.
Found this site with some info on the topic of boiling points of diffent fluids: