In the last post, we talked about some lines your auto mechanic might tell you to try to get you to do unnecessary service on your car.  This is Part 2.

Don’t Listen to Your Auto Mechanic if He/She Says:

Replace Brake Pads Every 30,000 Miles for Fronts, 60,000 Miles for Rears

I am absolutely shocked at how long brake pads can last nowadays.  Specifically, the factory pads.  The aftermarket pads I’ve tried have tended to have roughly the same lifespan as always, about 30,000 miles on the fronts and 60,000 on the rears.  You may have found a better brand than I have, though.  On my 2009 Venza, at around 35,000 miles, I pulled the front pads off because I figured I must be getting close to the wear sensor.  (That’s the light metallic squealing sound you hear as your brake pads are nearing replacement.  There’s a little metal clip on your brake pads that starts making contact with the rotor when your pads wear down to a certain point.)

Anyway, when I pulled the pads off, I was surprised to see that there was still a LOT of meat on the pads.  I swapped out the pads anyway, since I was there and wanted to try the aftermarket pads, but after about 30,000 miles, I switched back again.  Just a couple weekends ago, I finally wore down the factory pads on the front, and I’ve got 101,000 miles on my car.  That means the factory pads lasted about 70,000 miles on the fronts!

The reason this is so surprising to me is that brakes are pretty unsophisticated when it comes right down to it.  You’re essentially mashing a mix of metal and other things (the pads) against a spinning disc of metal (the rotors) and letting the friction slow the car down.  It creates heat in the process, and generally the faster you stop, the more heat is created.  I’m no engineer, but it seems like there’s only so much they can do to make that process better.  It’s not like there’s a computer that can optimize the process; it’s strictly mechanical at that level.  Nonetheless, somehow they’ve made the process way better.

Oh, and nowadays, if your rotors get warped after a long time, just replace them.  Older rotors used to be really thick, so if they got warped, you would just have your mechanic grind down the hilly spots to make them flat again.  Now rotors are thinner (probably to save weight), which means there’s not much to grind down, when it comes down to it.  Also, Amazon has rotors for about $40 each wheel, which is probably cheaper than the labor to grind down the old rotors anyway.  How do you know if your rotors are warped?  If your car is normally fairly quiet, but it develops a ton of squeaks and rattles every time you approach a red light, that might be a sign.  You can test it by coming to a complete stop, and then gradually lifting your foot off the brake, just until the car starts rolling.  Hold the brake in a steady position and see if you can feel the brake pads grabbing, and then not grabbing, and grabbing again as the wheel turns slowly.  If so, you’ve got a warped rotor, and should probably swap them out at your next brake pad change.

Flush and Replace Your Brake Fluid Every 30,000 Miles (or for Every Brake Job)

Again, this is one of those things where technology (or chemistry) has apparently improved significantly.  The old wisdom was that you should replace brake fluid about every 30,000 miles or so, about the time you’d be changing your front brake pads anyway.  The reason for this is because brake fluid is hygroscopic, meaning it pulls moisture from the air.  So over time, your brake fluid becomes more and more composed of water.  Water in brake lines is bad.  Not only can it cause corrosion of your braking components, but when water is subjected to the hydraulic pressures in the brake lines, it can heat up and turn to steam.  Steam is very bad.

Hydraulic braking systems work because liquid doesn’t compress.  You step on the brakes, and the liquid in the brake lines acts as a very good transferring mechanism to provide the same pressure you’re applying on the brake pedal to the brake calipers, which mash the brake pads onto the rotors.  If you replace the liquid with air, though, you’re hosed.  That’s because air compresses very easily.  So you can be pressing on the brake pedal, and if there is air in the lines, it will just squish down and not provide much pressure transfer at all to the calipers.  Your brake pedal can go all the way to the floor, and your brake pads might barely be touching your rotors.  That’s not good for stopping.

Many of the old blends for brake fluid would gather water pretty quickly, and might need to be replaced at around 30,000 miles before your braking system was too compromised.  Now, somehow, they have come up with blends that barely take up any water, and so virtually never need replacement.  My service manual has no recommended interval for brake fluid replacement.  Theoretically, it could last forever.  I just tested my brake fluid on the Venza with a test strip, and after 100,000 miles and 7 years, it still barely registered any water at all.  In fact, I’m wondering if my test strip was faulty, so I will probably buy a different brand of strip just to double-check.

If your service manual recommends replacement at certain intervals, go ahead and do it.  If it doesn’t, consider using a test strip to see if you need to flush the system, or just leave it alone unless you feel like your brakes are not as strong as they used to be.

Those Little Metal Shavings in the Transmission Fluid Mean You Need a Transmission Rebuild

This one is one of the oldest tricks in the book, and thankfully, it seems like it’s getting used less and less because people are changing their transmission fluid less frequently.  Back in the days when people had to replace their transmission fluid roughly every 60,000 miles, you’d take your car into the shop, and the mechanic would drain the fluid into a pan.  If the shop was slow or if your mechanic had a boat payment that was about to come due, he might bring the pan into the waiting area and show it to you.  “See the metal shavings in there?  That’s bad,” he’d say.  He’d try to convince you that your transmission probably needed to be rebuilt, and you’d think “oh shoot, well, I’m glad he caught it before it became a real problem.”

Here’s the thing: if it was a problem, you’d probably know about it.  Your car would be shifting roughly, or shifting really slowly (think a big pause between gears), or not shifting at all, and then you’d have something worth fixing.  The fact that the mechanic caught it before it became a problem really means that it wasn’t a problem at all.  What about those little metal shavings in the bottom of the pan, though?  If the metal shavings are small, and especially if it’s your first transmission fluid change, those are totally normal.  That’s why the drain plug in transmissions is usually magnetic, because it’s expected that there will be some fine metal shavings, and the magnetic drain plug usually keeps them out of the way.  If you have sizeable chunks of metal in your transmission fluid, that’s a different story.  But don’t be alarmed by little glittery pieces of metal shavings in the drain pan.

“We Legally Can’t Let You Leave with Your Car in this State; It’s Unsafe”

If you ever hear this, insist that they put your car back together as it was, and leave.  Leave on a tow truck if necessary.  There is no law that I have ever heard of that says that a car that you drove into the shop cannot legally be driven back out of the shop.  The auto mechanic is trying to intimidate you into leaving your car there and forcing you to do the work with them.

Even if the mechanic was willing to do the work at a reasonable price, and to do the work competently, I wouldn’t stay there based on principle after a statement like that.  The last thing you want in a mechanic is a liar, and that’s what they just did to you.  Your vehicle may be unsafe to drive.  Nonetheless, the “legal” argument to try to trap your car at the shop until you pay the ransom (i.e., whatever repair bill the mechanic feels like throwing your way) is nonsense.  Vote with your feet and get outta there.

Before You Buy Into Anything Your Mechanic Tells You, RTFM

If you’re unsure whether your mechanic is telling the truth about your need to flush the cooling system, or replace the air filter, or any number of other things, your first step is to read the frigging manual.  (Sorry, stepdad!  Sometimes reading the instructions is a good thing!)  The manufacturer of your car has a better idea of what’s required for it than a mechanic who might be stuck in the dark ages of car maintenance.

The second best thing you can do for yourself is to use your brain.  I know not everyone thinks mechanically, but give it a shot before you just believe anything your auto mechanic tells you.  If you can’t figure out whether it sounds necessary or not, Google it.  Or call a friend.  Or both.