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Without trying to toot my own horn, I know a lot about cars. I understand how most items on a car function and how they fail. I know the difference between a 6 ply tire and a bias-ply tire; I can talk about the pros and cons of direct injection; I can argue in favor or against anti-lock braking systems, etc.

Unnecessary fluid flushes.

Beware vehicle service professionals pitching fluid flushes...they're often a waste of money. In some cases, they can actually harm your vehicle.

This knowledge frequently causes frustration when I take my vehicle in for basic services like an LOF  (lube, oil, and filter), tire rotations, etc. and I’m “pitched” an unnecessary service item. While I know the service being pitched is a giant waste of money, the average consumer probably doesn’t know…and that makes me angry. Service professionals who recommend unnecessary services ought to have more respect for the consumer (and better ethics).

As a general rule, fluid flushes and/or replacements are unnecessary. Here’s a list of maintenance items that involve a fluid flush/replacement and guidance on whether or not to pay for each.

Power Steering Fluid Flush – These are rarely – if ever – necessary. Power steering fluid will become dirty and smelly over time, but it will remain functional for the life of most vehicles. Unless your vehicle manufacturer recommends changing this fluid (and very few of them do), or your power steering system is giving you trouble, there’s simply no reason to bother with a  power steering fluid flush.

Brake Fluid Flush – Brake fluid is hydrophillic, which means it sucks up water like a thirsty camel. Brake fluid can even pull water out of the humidity in the air. As brake fluid sucks up moisture, it loses effectiveness. If it absorbs enough water, brake fluid can even “boil over” during normal use.

Modern brake systems are sealed

Modern brake systems are completely sealed, so brake fluid rarely (if ever) needs replaced. Image courtesy

In light of brake fluid’s sensitivity to water, automakers go to great lengths to ensure your brake system is completely and totally sealed. Therefore, the average vehicle never needs replacement brake fluid. Unless you’re doing a LOT of heavy braking (racing, towing a heavy trailer on a regular basis, etc.), your brake fluid will last as long as the system remains sealed. It’s almost always unnecessary to flush brake fluid.

Coolant Flush – Many vehicles use long-life engine coolant, which has a typical life expectancy of 150k miles. Some still use “conventional” coolant, which only has a 30k mile life expectancy.

To determine if your car needs coolant flushes every 30k miles or every 150k miles, check your vehicle manufacturer’s scheduled maintenance booklet. Follow the interval suggested – no more and no less.

Automatic transmission fluid flushes.

Do not flush the fluid in a sealed automatic transmission. It can do more harm than good.

Automatic Transmission Service/Flush – Last but not least, automatic transmission services are often completely unnecessary. Most new vehicles use synthetic transmission fluid that can last the lifetime of the vehicle – meaning that you’ll never, ever, EVER have to change it. Just check your vehicle’s maintenance booklet…if you don’t see a recommended transmission service interval, than your transmission doesn’t need service.

NOTE: Another clue that your transmission doesn’t need service? There’s no transmission fluid dipstick under the hood. Most automatic transmissions with lifetime fluid are “sealed,” meaning there’s no way to change the fluid.

When I’m told by my local shop that my transmission needs flushed, and I reply that the transmission uses a lifetime fluid, the person I’m talking to will often tell me that replacing my transmission fluid “couldn’t hurt.” This is completely and totally incorrect. Replacing the fluid on a transmission that doesn’t require fluid replacement is a delicate procedure. If it’s done incorrectly, damage is likely.

If you take nothing else from this article, remember this: Unnecessary transmission service can cause transmission failure.

Beware “Power” Flushes – For a time, “power” fluid flushes were popular. The thinking was that forcing fluid through your vehicle’s transmission, cooling system, etc. would be more beneficial than simply draining and replacing fluid.

Unfortunately, it took a while for auto service professionals to recognize that “power” flushes often do more harm than good. Power fluid flushes have caused leaks in cooling, steering, and braking systems, and they’ve ruined thousands of automatic transmissions.

If your local shop wants to “power flush” something, find another place to get your service done. Power flushing is unnecessary, and in many cases it can cause a failure.

*NOTE: I realize that some of you might argue that a true enthusiast changes their own oil, rotates their own tires, etc. Maybe so. I’ve learned that it takes me longer (and therefore costs me more money) to do these things myself. I’m also lazy.


About the author: Jason Lancaster


Jason is the editor and founder of,, and a handful of other automotive enthusiast websites. When Jason isn't writing about cars, he's playing or watching basketball, hanging out with his family, and finding new ways to waste his hard-earned dollars on his car.


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  1. Brian Flewelling

    You are an idiot, where do you get you facts, is hydrophylic a word how about hyrdoscopic as in brake fluid.
    I suppose you don’t need to change you engine oil either, waste of money.
    All fluids get contaminated and break down over time.
    fluid replacement is cheap insurance, maybe you need to talk about cost of ownership after the warranty is over, because the OE is only concerned you make it to that mark and “low”cost of ownership sells more cars


      On the contrary Brian, GM put out a technical service bulliten regarding the flushing of fluids, saying NOT to do this as it could harm the vehicle. Sure some fluids are ok and important, but not in newer model vehicles. Its a waste of money.

    • Right on Brian! In addition all this when our government decided to put the annual maintenance cost on new car window stickers. Over night we had “lifetime” fluids. A new BMW still gets brake fluid changes every two years. Which means under the maintenance agreement they pay for it during the lease. Thanks for your comments!!

  2. Pingback: Tips on when I change my brake pads on my own? - Page 2 - Hyundai Forums : Hyundai Forum


    Use common sense with anything you encounter. If you don’t understand, you are probably someone who spends more than a few minutes per day playing with their “smart” phone.

  4. Thanks for the great post, Jason! It’s very refreshing to see someone speak the truth about what does and doesn’t need to be done as car maintenance. Most repair places have ZERO integrity when it comes to recommending unnecessary maintenance. I appreciate you sharing the truth with those who are unaware.

    Brian F.: hy·dro·phil·ic /hīdrəˈfilik/
    (adjective) having a tendency to mix with, dissolve in, or be wetted by water.

  5. @Brian Flewelling. Why are you attacking the author? Why should anyone trust you, when it is clear that you did not even make an effort to look-up the dictionary for the meaning of the word ‘hydrophilic’ – YES IT IS A WORD.

    Yes it is true that ‘most’ OILS breakdown. (Water is a fluid it doesn’t breakdown naturally). But newer synthetic oils/fluids last longer and improvements in design and technologies make some services in modern cars unnecessary.

  6. Jason Lancaster

    @Brian – As others have pointed out, hydrophilic is a word. :)

    Your comment that fluids break down and get contaminated over time is correct. The question is, how much time?

    Many fluids used in automotive applications (like transmission fluid, steering fluid, and brake fluid) are used on semi trucks. In many cases, these *identical* fluids have a 150k-400k miles of life, depending on how the vehicles are utilized.

    Considering that automatic transmission fluid in a semi can last 300k miles, it makes sense that automakers seal transmissions. There’s no reason for anyone to flush that fluid, as it will last longer than the car itself.


    As a service professional for over 25 years, I can tell you why you are being asked to flush all the fluids in your vehicle. As car manufacturers started making cars MUCH better, the dealers needed a way to keep the doors open. It costs a fortune to run a dealership service department. So, they came up with “flushes” All of a sudden, cars need to be flushed. Quite simply, if the service personel doesn’t do this, the management will fire them and find sombody else that will. That’s it. All your getting is your wallet flushed to pad the books.

  8. Pingback: Beware of "Power" Flushes - ATFonATF

  9. Mark Floyd

    The correct term is hygroscopic – as in absorbing or attracting moisture from the air. whereas hydrophilic, tending to dissolve in, mix with, or be wetted by water:
    The expected life of an automobile is still 100,000 miles in the eye of the manufacturer – in that lifetime fluid flushes are rarely needed, but the cars we see have well over 100,000 miles, some as high as 300,000 with the average approaching 200,000 miles. fluid flushes are necessary to obtain these high mileages.
    “Many fluids used in automotive applications (like transmission fluid, steering fluid, and brake fluid) are used on semi trucks. In many cases, these *identical* fluids have a 150k-400k miles of life, depending on how the vehicles are utilized”. Semi truck systems are also 10 times larger holding 10 times more fluid and operate at a much lower RPM than automobiles. as a comparison I see the need to change fluids in an automobile at the same rate divided by 10?
    The automobile manufacturers are the ones who started the flushing programs as a warranty requirement, now that cars are lasting longer they say no.

    • Jason Lancaster

      Mark – Thanks for commenting.

      You make some great points about the problems with comparing big truck maintenance and normal vehicles, and I agree on your point about the proper word to use (hygroscopic). Thank you.

      As for fluid flushes being necessary after some arbitrary mileage or time period, I strongly disagree. Fluid life isn’t determined by time or mileage – it’s determined mostly be exposure to heat and oxygen, which may be frequent on some vehicles and infrequent on others. Where a lot of service professionals run into trouble is to assume that they “know” a fluid is bad just because it’s old or has a lot of miles. I’d submit that I can ruin brake fluid in less than 2k miles as easily as I can preserve it for 200k miles, so it very much depends on use and the driver.

      But if we’re talking about *average* drivers in *average* types of use situations, flushing a fluid just because it’s old makes little sense. Steering fluid doesn’t need to be replaced merely because it’s looking dirty. Brake fluid doesn’t need to be replaced unless it’s boiled over or been exposed to extreme heat. Transmission fluid doesn’t need to be replaced at all, at least if it’s a lifetime fluid.

      When service professionals stop offering guidance on fluid replacement in arbitrary, absolute terms, we won’t have to talk about this problem any longer. But until then, I strongly caution anyone from paying for a brake, steering, or transmission fluid replacement that’s not part of the manufacturer’s recommended maintenance schedule.

  10. Mark Floyd

    I do agree about the manufacturers recommendations and I no longer recommend replacement based on age or mileage but by looking, feeling and smelling the fluid with practiced knowledge that better assesses the condition of the fluid. if the fluid is indeed very dirty, oxidized, contaminated or in the case of brake fluid has to much moisture in it they need to be replaced. brake fluid testers are made to perform this test. to make a blanket statement that these fluids never need to be changed is very misleading as is replacing just because of mileage. what needs to be said is that you should fine a reputable mechanic that is going to assess your cars needs based on fact not arbitrary guidelines. I have seen many failed ABS and brake components because the moisture content was to high causing corrosion. Failed transmissions because the fluid was burnt, cooling systems corroded through because the antifreeze was very acidic. the only way to prevent this is through proper preventive maintenance. as you said you can ruin brake fluid in 2k miles. people think how they drive is average – no matter how they drive. we need to assess on a per car basis only.

    • Jason Lancaster

      Mark – If every technician were as reputable as you seem to be, I’d be inclined to agree. :)

      Unfortunately, most of the dealerships I know of and many of the independents I’ve been to in my life have recommended unnecessary maintenance. When probed for specifics, the answer isn’t “we have reason to believe that your brake fluid has a lot of moisture in it because…” or “your coolant is too acidic,” etc., it’s been “well…it couldn’t hurt,” or “100k miles is a long time.”

      Furthermore – and no offense to you – but NO ONE can tell by looking or feeling if a fluid is bad. Brake fluid testers are often wrong, and smell tests can be deceiving. What we need is fluid analysis, similar to oil analysis, but that’s not the standard process, and I’m not at all sure that any company offers testing of these “other” fluids.

      I agree that fluid can cause failures, but I’d submit that there are plenty of other indications of a problem besides fluid look/feel/smell.

      As I said, I think consumers should be very careful paying for fluid replacements. If the replacement isn’t suggested in the manufacturer’s maintenance guide, the technician ought to have a very good explanation as to why these lifetime fluids need to be touched.

      • You can most certainly tell if a fluid is bad by smell and visual inspection. By “bad” of course I’m not referring to viscosity properties or molecular break down but bad as in you don’t want it in your vehicle. I wouldn’t say it was garbage, but you may want to filter it somehow if this makes sense, otherwise, chuck it! In respect to ATF, different manufacturers have different fluid specs so you could have the wrong fluid in a GM trans and consider it “bad” based on it’s properties. My definition of bad would be contamination to which is usually visual whether it’s burnt clutch material, varnish from oxidation, or flakes of metal. Bad = contaminated

  11. Great converation going on here. Lots of good points. Unfortunately there is NO way to tell if a fluid is good or bad just by looking at it (unless it’s cloudy/milky-then it has water in it). An oils job is to keep broken down medal fragments away from the moving parts. It’s looks dirty becasue it’s doing its job. Oils will smell differenly based on the additived used in the formulation. I can’t tell you how many times I’ve tried to guess whether an oil is good or bad by looking at it….and been wrong. It’s what I do for a living. The only real way is to send a sample in for analysis. Unforunately no one is going to do this with ATF. So Just follow the guidelined in the maintenance section of your owners manaual. If you drive a lot and start to get shimmer at high sustained speeds and you’ve never changed your ATF and your owners manuals says it should be changed… then change it. If you don’t notice any issues, you are probably fine.

  12. Well I don’t have much to add to this conversation other than 17 years of transmission experience but it may help. Hydrofallacy was it? Haha, who cares. Newer trans use special fluid that is considered “lifetime” fluid as in once it’s time to service the fluid, an overhaul is needed and they should be done together. That it was lifetime means references, now what could determine the lifetime of a trans? Excessive heat from the torque converter or inadequate lube which could stem from debris (clutch material, varnish, oxidation, etc.). Sometimes water can find it’s way into the fluid through open vents or driving through puddles, rain, etc. FLUSHING is a big no-no because a lot of transmission debris that the filters can’t pick up tend to find little hiding places to accumulate in the trans either electrostatically or just from the flow of pressure within the valve body. When back flushed, this otherwise benign debris gets stirred about like a snow globe and opens up all sorts of new possibilities to travel and score up valve bores causing valves to hang up or stick, solenoids to plug, or they can become embedded in the clutch material themselves which reduces the friction coefficiency. It also creates the perfect scenario for a lube shop to install or mix improper fluid for specific trans requirements which can cause erratic operation. The best part… can NEVER get all of the fluid out of a transmission by any means of flushing no matter what anyone tells you, this is mostly due to the valve body and torque converter which likes to hide fluid. The best suggestion would be to install a couple magnetic inline filters, drop the pan and change the internal filter and refill with factory recommended fluid. The external filters are MUCH easier to maintain and service and will keep the internal filter from clogging prematurely because they have a better micron rating, as in they filter out smaller particles that the internal trans filter simply can’t in able to maintain proper pump suction. IF your fluid is dark but your trans is operating just fine, install an inline filter and see if your fluid improves by removing smaller particles that darken fluid. Proper fluid is just as important as clean fluid for correct operation of the valve train and solenoids. I wouldn’t worry about the fluid “breaking down” unless the trans has been operating at abnormal temperatures to which the fluid isn’t the problem but is most likely a result of poor lubrication or cooler flow.

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