When it looks like this:
Man that is really dark! Mine is not even close to that color. More like sort of apple juice color
Man that is really dark! Mine is not even close to that color. More like sort of apple juice color
dave_the_nerd
Lifer
- Feb 25, 2011
- 16,991
- 1,620
- 126
BoomerD
No Lifer
- Feb 26, 2006
- 65,902
- 14,301
- 146
Brake fluid is hygroscopic...it absorbs moisture (water) from the air. (remember, your brake fluid system isn't air-tight) That moisture can cause components to rust...and it can boil at MUCH lower temps than good brake fluid...leaving you with NO brakes.
I've always changed mine at approx. 2-3 year intervals. (check your owner's manual for factory recommendations)
I've always changed mine at approx. 2-3 year intervals. (check your owner's manual for factory recommendations)
dave_the_nerd
Lifer
- Feb 25, 2011
- 16,991
- 1,620
- 126
So, I have owned three Honda Accords with over 250,000 miles on each one. Never replaced the brake fluid. Never took the "cap" off to look at the fluid. Never had any issues with my brakes. Never had any calipers fail or the master cylinder fail on any of them. All I've ever done was verify the fluid was between the MIN and MAX marks. So, could it be that since I never exposed the brake fluid to air, is that what kept it from accumulating moisture and not causing any issues? I never felt like the brakes were "spongy" or felt "off". With three cars with high mileage and no brake issues, I'm not convinced it's necessary.
mindless1
Diamond Member
- Aug 11, 2001
- 8,723
- 1,735
- 126
^ I agree but there are a number of factors, and I don't pretend to be able to recall them all at this moment.
1) Some braking systems have more margin than others, especially since the advent of ABS where the brakes could be designed far more powerful (and touchy) then let the computer save the driver if they overapply.
2) Similarly, wheels on any particular sized vehicle got larger so larger diameter rotors would fit, also helping achieve braking performance with less pressure.
3) The idea is the fluid is hygroscopic and absorbs moisture so yes, not taking the cap off the reservoir can't but help (to some minor degree) but the truth is, there is a maximum amount of water that any of the DOT fluids can absorb and while someone fascinated with numbers will point out that this lowers the boiling point, it comes back to what the braking system in the specific vehicle, under the specific driving cycle scenario is exposed to and how much heat that generates.
4) If driving like you just robbed a bank, or down steep long hills or worse hauling/towing a load (more so the closer you get to the max vehicle weight rating), you more likely reach a critical temp threshold where however much water there is in the fluid, boils and creates compressible air and the more it impedes a safe stopping distance.
SO, if you are pushing the limits for the vehicle design, it matters more and more. Some will also say it corrodes the brake lines from the inside out, but I never found that to be a primary line failure cause. In a climate where there are never salted roads, it might matter over 30 years but in other regions, lines are as likely to rust from the outside in rather than the inside out.
Most people do not flush their brake fluid on a schedule and some manufacturers don't even include a brake flush interval, not even past 100K mi, so clearly they do not think it is necessary or else there would be a massive recall for their vehicles crashing to to brake failure from lack of maintenance, remembering it is usually past the warranty period so no expense on their part to shift the burden to the customer and also add income to shops doing it to adhere to service intervals.
My take on it is to drive conservatively and if you notice braking problems, leave no stone unturned to figure out why. If you refuse to drive conservatively, replace the fluid, replace a dozen or more things because you're ragging the vehicle out and need utmost performance to compensate for that driving style.
Moisture in fluid is a progressive thing so with conservative driving one should notice an issue before it's bad enough to cause a problem, but at the same time if I had very old fluid and were suddenly going to haul much higher load or go on vacation towing a camper or heavy boat down steep hills, I would flush the fluid first on a truck or SUV... cars, not so much.
Main thing is, do what works for you. If it is under warranty and fluid flush is spec'd, go ahead and do it as it is not expensive and better to preserve the warranty than avoid this minor expense.
Personally I suspect that by the time the average car needs new fluid to be "safe", if ever, it is also time to replace at least the soft brake line hoses and in doing so, they will be flushing new fluid through anyway. At the same time, consider that if you DIY things, a replacement brake line or caliper isn't very expensive but if you let a shop do the work, new lines and calipers can be far north of $1K so the other factor is when there an eventual brake problem (all things wear over time), do you have a large expense at that point, which may be as much as the vehicle is worth if paying someone else to fix it at that point.
I mentioned miles above but clearly all miles are not the same. Highway cruising is very easy on brakes while stop and go city driving, not so much.
1) Some braking systems have more margin than others, especially since the advent of ABS where the brakes could be designed far more powerful (and touchy) then let the computer save the driver if they overapply.
2) Similarly, wheels on any particular sized vehicle got larger so larger diameter rotors would fit, also helping achieve braking performance with less pressure.
3) The idea is the fluid is hygroscopic and absorbs moisture so yes, not taking the cap off the reservoir can't but help (to some minor degree) but the truth is, there is a maximum amount of water that any of the DOT fluids can absorb and while someone fascinated with numbers will point out that this lowers the boiling point, it comes back to what the braking system in the specific vehicle, under the specific driving cycle scenario is exposed to and how much heat that generates.
4) If driving like you just robbed a bank, or down steep long hills or worse hauling/towing a load (more so the closer you get to the max vehicle weight rating), you more likely reach a critical temp threshold where however much water there is in the fluid, boils and creates compressible air and the more it impedes a safe stopping distance.
SO, if you are pushing the limits for the vehicle design, it matters more and more. Some will also say it corrodes the brake lines from the inside out, but I never found that to be a primary line failure cause. In a climate where there are never salted roads, it might matter over 30 years but in other regions, lines are as likely to rust from the outside in rather than the inside out.
Most people do not flush their brake fluid on a schedule and some manufacturers don't even include a brake flush interval, not even past 100K mi, so clearly they do not think it is necessary or else there would be a massive recall for their vehicles crashing to to brake failure from lack of maintenance, remembering it is usually past the warranty period so no expense on their part to shift the burden to the customer and also add income to shops doing it to adhere to service intervals.
My take on it is to drive conservatively and if you notice braking problems, leave no stone unturned to figure out why. If you refuse to drive conservatively, replace the fluid, replace a dozen or more things because you're ragging the vehicle out and need utmost performance to compensate for that driving style.
Moisture in fluid is a progressive thing so with conservative driving one should notice an issue before it's bad enough to cause a problem, but at the same time if I had very old fluid and were suddenly going to haul much higher load or go on vacation towing a camper or heavy boat down steep hills, I would flush the fluid first on a truck or SUV... cars, not so much.
Main thing is, do what works for you. If it is under warranty and fluid flush is spec'd, go ahead and do it as it is not expensive and better to preserve the warranty than avoid this minor expense.
Personally I suspect that by the time the average car needs new fluid to be "safe", if ever, it is also time to replace at least the soft brake line hoses and in doing so, they will be flushing new fluid through anyway. At the same time, consider that if you DIY things, a replacement brake line or caliper isn't very expensive but if you let a shop do the work, new lines and calipers can be far north of $1K so the other factor is when there an eventual brake problem (all things wear over time), do you have a large expense at that point, which may be as much as the vehicle is worth if paying someone else to fix it at that point.
I mentioned miles above but clearly all miles are not the same. Highway cruising is very easy on brakes while stop and go city driving, not so much.
Torn Mind
Lifer
- Nov 25, 2012
- 12,046
- 2,763
- 136
I would suspect that use and heat allows for drivers to neglect their brake fluid for the "lifetime" of their vehicle. The steel inside the lines are corroding but perhaps the constant flow and heat counteracts the process. Factors like climate and chemicals used to deal with climate(salt) may also play a factor.
OEM quality fluids may have better additives as well. When I swapped out the OEM Toyota fluid in my mom's car after say, 7-8 years, the color was not pronounced at all. But when I swapped out cheap Supertech fluid after only three years, it was a vibrant, and dare I say appealing, looking green.
Castrol's formulation is apparently designed for old British vehicle with vented systems, so it would supposedly have greater longevity than cheap Supertech.
OEM quality fluids may have better additives as well. When I swapped out the OEM Toyota fluid in my mom's car after say, 7-8 years, the color was not pronounced at all. But when I swapped out cheap Supertech fluid after only three years, it was a vibrant, and dare I say appealing, looking green.
Castrol's formulation is apparently designed for old British vehicle with vented systems, so it would supposedly have greater longevity than cheap Supertech.
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