Is changing brake fluid really necessary?

CAR TALK

Dear Car Talk:

Help! After almost 60 years of driving, I have two questions that have me puzzled. On my new 2018 Nissan Murano, they are recommending a brake fluid change every 30,000 miles. I have never heard of this — I thought that other than adding fluid due to a leak, this closed hydraulic system fluid would last the life of the car. Is this a necessary item, or just a way for the dealer to make money? Secondly, the vehicle came with synthetic-blend motor oil with a 0W-20 viscosity rating. When I change the oil for the first time, I am planning to use 5W-30 HD non-synthetic oil, as I always did with my 2006 Murano that I just traded in. Can I do this, or must I always use the synthetic blend that the vehicle came with? Thanks. — Tony

I’ll answer your oil question first, Tony: You should use the synthetic oil. It’s better oil. It provides better lubrication; it’ll give you better mileage and better longevity.

Your TV is bigger and sharper than it was in 2006. Your phone is smaller and more powerful than it was in 2006. The oil in your car is better now, too. Plus, the engineers and technicians at Nissan, who have a combined 32,700 years of college education, figured out the tolerances and the lubrication requirements for your engine, and if you use some thick, old sludge in there, you could harm the engine and void the warranty. So use the recommended oil, Tony.

Regarding the brake fluid, lots of manufacturers are now recommending that you change the brake fluid every 30,000 miles.

It’s not a completely closed system. As the brake pads wear out, the fluid level drops, and some air must get in there to replace that lost fluid. There’s moisture in that air, so the brake fluid has to absorb the moisture to keep water from rusting the brake lines, the master cylinder, the caliper pistons and your ABS (antilock braking system) components. So eventually, the brake fluid will need to be changed to protect those parts.

Whether 30,000 miles is the longest you can go, I don’t know. We do sometimes see cars with 150,000 miles on them with their original brake fluid. But I can’t recommend that approach to you.

First of all, most of those cars have had a “de-facto” brake fluid change somewhere along the way, when they sprung a leak or had major brake work done.

Second, the risk with old brake fluid is that it gets saturated with water and can no longer hold enough water in suspension. Then the water starts to corrode your brake components. You probably can guess what happens after that (it ends with a brake pedal that goes to the floor and you uttering a two-word phrase, of which the first word is “Oh”). Or, if you’re lucky enough to catch it earlier, you’ll end up spending hundreds of dollars to replace brake parts, and using that same two-word phrase when you see the bill.

So I would say if it’s not prohibitively expensive — and I’d say the job should be in the neighborhood of $100 to $150 for an average car — it’s a small price to pay every 30,000 miles for peace of mind.

Enjoy your new car, Tony. And welcome to the future.