While I recognise the the brake system in my car is redundant, is it possible that failure to replace brake fluid could result in a fatal accident? or is there sufficient redundancy and warning systems in place that the operator of the vehicle would at least notice that there is a problem to have it addressed?

I ask as I just found out that my dealer, although required to replace brake fluid every two years regardless of mileage according to the service schedule, hadn't been doing it, ever (I have owned the vehicle for almost eight years now) so want to see if this is something that is simply a maintenance cost issue or a life safety issue.

My guess is it could result in corrosion of the components (as the corrosion inhibitors would be used up) and both hydraulic systems would likely corrode at a similar rate, potentially resulting in near-simultaneous failure, though that could take a while, and might be unlikely.

Are they putting lives at risk by failing to change brake fluid? Is it a big risk?

2 Answers 2


YES. A big Y-E-S. It's a huge safety issue. See, braking fluid absorbs(even attracts) water over time, not so much over usage, if at all. Brake fluid gets really hot, even more under sustained braking like when driving in the mountains. If there's water in the system, it'll try to evaporate. This causes vapor locks, pedal/braking pressure falls away, etc. The longer the water sits, the more it can corrode things in the brake system. It can weaken the pipes and cylinders. In short, all kinds of scary things can/will happen if the fluid isn't changed per advice of the manufacturer. Waiting 3 instead of 2 years likely won't do much harm, but fluid is cheap so I wouldn't take the risk.

There is redundancy in the design, but that should absolutely not be seen as play room. Other things can fail or weaken without sign, and that's what this redundancy is meant for. This above is based on you using non-silicone fluid (DOT4, 5.1 etc.) If you use DOT5, different advice may apply, which should still be taken seriously.

  • Agree with that - also, I'd advise changing mechanic! Apr 4, 2018 at 22:37

As somebody who has driven an over 20 year old rarely driven car, I can say that brake feel after brake fluid replacement was much better than before brake fluid replacement. Based on this, I tend to believe the recommended replacement intervals are correct. The car had only 40k kilometers when I started to drive it and I accumulated only 40k additional kilometers!

Was I taking a huge gamble by driving such an old and rarely driven (and rarely serviced) car? Who knows, I wasn't driving on mountainous roads.

I would say that the things you should change based on time and not only on kilometers should include at least brake fluid, engine oil and timing belt. Brake fluid because it tends to absorb water. Engine oil, because less driven cars are typically driven for shorter trips and short trips are harmful to the engine oil. In some cases (very rare very long trips) you could perhaps extend the engine oil replacement interval, but not the brake fluid replacement interval. Timing belt, because rubber deteriorates as a function of age and timing belt snapping can result in catastrophic engine damage.

There are things that can be changed only based on kilometers, such as spark plugs. Brake fluid isn't one of them!

  • I agree with the oil and plug stuff, but why the belt? It isn't exposed to sun light or heat when not driven, so those don't affect its aging. I get it that still it deteriorates more or less over time, but I suppose km's do have much more unfluence on the aging. Well, it doesn't apply for me anyway, #timingchainmasterrace XD
    – Bart
    Apr 6, 2018 at 15:02

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