Brake Fluid Change Frequency: yearly?

I know a lot of people say to change it yearly, but I have an electronic brake fluid tester, one that even recognizes different brands and DOT types, and the fluid in my 997.2 and 987.2 both measure perfectly. So do they truly need to be changed? I put about 5,000 miles per year on both cars.

Porsche recommend brake fluid flush every 2 years, not annually. Track guys may do it more often since they cook their fluid, but no reason at all for doing it more frequently otherwise. The reasons its done, even if you put one mile a year on it is because brake fluid is hygroscopic and absorbs moisture from its surroundings which will corrode the internals of the brake system, but I'm sure you are already aware of this if you have a fluid tester. I wouldn't have any issue waiting even longer than 2 years if its testing properly since the water absorption is the entire point in the first place, and owners in different climates may have different results and needs. I'm sure Porsche assumes no one is bothering to test, so they use a blanket 2 year interval to cover all bases

I totally get the recommendations from Porsche , and most other car manufacturers, about changing brake fluid regularly, flushing trans fluid on schedule, replacing serpentine belts at certain mileages, etc. And if I had deep pockets I would be more than happy to shell out massive amounts of cash to meet these service schedules. But in the real world, after having owned 50+ vehicles, I think I changed brake fluid in two of them, never flushed a trans, and only change belts when inspection warrants their replacement. Despite this scoffing at these suggested service intervals, I’ve never had any issues with the aforementioned systems. One of the few times I took my ‘08 Boxster to my Indy to replace the rear main seal, only because I’m not fortunate enough to have a full-on lift in my garage, he changed my serpentine belt for the hell of it at +50k miles and returned the old one. He even noted that it looked like new and suggested I keep the old one as a spare. A friend that owns a Jaguar always comes home from the dealership with a several page invoice for trans flush, $800, brakes (even though she barely drives 300 miles a year), and various other upsells. The way I see it, ’if it ain’t broke, don’t fix it’. YMMV.

A +1 on what ICNU said. And I hope to never buy a car that was maintained by WTFChuck. 🤣 I keep my cars sometimes for decades. And my daily is approaching 300,000 miles. Still running great. I attribute that to following a reasonable maintenance schedule. Of course, reasonable can vary depending up lots of factors with the environment and climate as well driving environment. A car driving a short distance in New England is going to need much more frequent maintenance that one driven 15 miles each way to work in NC.

Unless you are draining some fluid from each caliper and testing it, what you get from the reservoir might not tell the whole story. If you are going through the trouble of getting a sample out from each caliper, you might as well flush it. Moisture can come in multiple ways and you are probably only checking the clean stuff in the reservoir. The seals on the calipers are going in and out and there are probably 4-6 seals per caliper going in and out, pulling small amounts of moisture over time. Rubber hoses supposedly can still let some in too. So just change it every two years or so and be done with it.

As I age it’s getting less fun to flush the system. However, since I have a great garage and other than no lift a competent tool shop? I get it ready day one, in the air, on stands, wheels off. Then day two flush it more than necessary and reassemble. Am I sore after? Yeah worse than ever but I also trust my work and although I have no idea I’m going to assume even an Indy price would be sobering to a guy who has never paid for one.

You won’t have to worry about that. I’ll put you on my ’do not sell to list’. Hope you are a better mechanic than you are a stand up comic. One visit to my garage will prove that to you 😱 Hmmm, let’s see. Over 50+ cars, no problems, one going over 350,000 miles is proof enough. Dealerships love your kind. They probably rub their hands together when they see you pull up. Just bring a credit card with a high credit limit. My record speaks for itself. Do you change your own oil? Or do you pay dearly for that privilege? By the way, people wait for me to sell my car to them. No need for you to get in that line.

Great responses, guys. The theoretical and then there's real life. Brake fluid is very hygroscopic and needs attention. For years, I couldn't never do a solid brake bleed -- even with speed bleeders on my motorcycle. However, I've gotten better at it. Now that I invested in a used Motive brake bleeder and a Quick Jack , brake fluid changes are really easy and aren't a big deal anymore. For years with all of my vehicles, I admittedly went without brake fluid changes and but knocked those out when the brakes felt soft. Unfortunately, remaining softness I think isn't from air but from older hoses -- which necessitates stainless steel hoses which makes a difference. These days, it's more of "when can I get to it" as opposed to actual difficulty. Having the right tools for the job makes all the difference. However, I currently have too many auto/moto projects that I'm working on where simpler things like oil changes absolutely take precedence. When (if) life settles down next season, I'll be doing both P-cars. TLDR; my thinking is that if you have the time and money, invest in a Motive (at least) and give it a whirl as it's the next step after doing oil changes IMHO. It's really not that hard if you have the right tools and the time to make it happen. Yet again, Quick Jack FTW where all four wheels are off the ground at once and you don't even have to remove the tires to do the brake fluid change. YMMV.

Chuck, we are in agreement about getting work done at dealerships. The overcharging is out of control. The OP wasn’t asking about doing a brake flush at a dealership versus an indie versus DYI. They were just asking about the maintenance interval. I stand by the need to perform brake flushes and other maintenance on cars.

Can you tell me about the tester. My cheap one just does moisture content.

Sorry for my sass. I too have a brake bleeder and Quick Jacks. My only point was that I am all over my cars weekly, having just come in from the garage topping off tire pressures, fluids, and a general once over of five vehicles. I base my needs on the seat of my pants, and my feet on the pedals. If my brake pedal feels squishy, I flush them. But if it is rock solid and performs well I go with my instincts and my history. I just feel that some of the recommended service intervals are meant to separate me from my money. I’ve heard that if a trans is performing well, a flush can cause more problems than it is meant to cure. If I had unlimited time and endless funds I too would ramp up on maintenance but what’s worked for me all these years is what I stick to. And on that note, I just discovered that I will be replacing the rear brakes on my Land Rover Defender in the next week or so as soon as I order new pads and rotors. The To-do list never seems to shrink.

The issue with nor replacing brake fluid on a decent schedule is that by the time you notice anything, yiu need a lot more than fluid. That is double for ABS systems. There is nothing magic about 2 years (probably the shortest needed if nor racing). 3 is better than 4, 4 is better than 5. As for transmissions there are definitely problems growing at the very first hint. The "don't chang the fuid, it causes problems is sn old wives' tail. It is supported by people who ignore the transmission till they start feeling "something", then change the fluid and when it dies they blame the new fluid. As an engineer at ZF once told me, there is nothing old fluid does better than new fluid. The recommendation was to change the fluid at 40k miles (new clutch material wears more than well used) then about every 80k there after.

This one also does moisture content, it simply has settings for exactly which brake fluid you run. It wasn't expensive, either.

There's no question that it's much better to do preventive maintenance, but again - it's more of a question of time and tackling them on one's "to do" list. I continue to enjoy multiple vehicles (cars/motorcycles/Vespas -- nothing terribly expensive, BTW), but one small reason I'm continuing to "thin the herd" as it were is that my time and energy is admittedly spread too thinly on the maintenance end of things -- I'm busy enough as it is and my physical energy admittedly isn't what it was when I was young. My own past year has been all about either "properly prep a vehicle for sale and sell it" and "a vital vehicle needs service so fix it ASAP." Once all that dies down, it'll likely be "brake fluid and oil changes week for every vehicle" in the stable. I'll have to check out that tester, @theblooms - Do you have an online link to it, BTW?

A slightly off-topic question for you fellow DIY brake guys. How do you dispose of the used fluid (and any left over in opened cans). I've got a few quarts setting in my garage nicely aging. I guess I could use some as paint remover.🤥

If you are changing often enough a well sealed can should be just fine (test first)

I have an oil reclamation center, I add it into the recycle oil. Not sure that’s kosher but I’m confident worse goes into the reclaimer.

Amazon.com: BELEY Brake Fluid Tester Digital Automotive Moisture Boiling Point Detector for DOT3,DOT4,DOT5.1 Brake Fluid with 2.8" Display, Audible Alarm, High-Precision Probe B10 : Automotive Amazon.com: BELEY Brake Fluid Tester Digital Automotive Moisture Boiling Point Detector for DOT3,DOT4,DOT5.1 Brake Fluid with 2.8" Display, Audible Alarm, High-Precision Probe B10 : Automotive www.amazon.com

Gets disposed of with my used engine oils.

Where I live the county dump accepts used oil. They have a separate area specifically for paint, chemicals and brake fluid. Although lately I’ve been sending my Castrol SRF back to FCP . Very pricey stuff and it’s great to use their lifetime replacement plan.

I've been using the new-ish Bosch ESI6 brake fluid in all my cars for the past few years. It exceeds DOT 4/5.1 specs and has a 3-year change interval. It's appropriate for pretty much any car that uses glycol brake fluid, even the ones that spec low viscosity fluid. It's not even that expensive (~$20/qt.) It's not very humid where I live and even after 3 years it's appeared to be okay moisture-wise when I've tested it, but brake fluid is easy enough to flush so I just do it on a 3-year schedule.