Buying guide for Best DOT 3 brake fluids
Despite the introduction of more modern versions, DOT 3 remains the country’s most popular brake fluid. There’s a common misconception that the newer DOT 4 and DOT 5 are more advanced, but that’s not entirely accurate, and there are good reasons you might be better off sticking with DOT 3.
Key considerations
Brake fluid 101
Hydraulic systems, like the one used for the brakes in your vehicle, need fluid to generate pressure. Water isn’t a good choice because it causes rust and boils too easily. Your brakes can hit over 350°F with ordinary road use, and as much as 1,000°F under heavy loads like racing. Petroleum-based oils are often used in machinery, but brake fluid uses a combination of solvents, lubricants (often synthetic), and corrosion inhibitors. These components also make sure the brake fluid doesn’t freeze.
DOT system: The DOT (US Department of Transportation) system of numbering brake fluid started with DOT 1 and DOT 2, but both are now obsolete. That makes DOT 3 the “baseline” product, but there are also DOT 4, DOT 5, and DOT 5.1. What are the differences?
Mostly it’s about boiling point, and DOT standards quote two: dry boiling point (when new), and wet (degraded) boiling point. The latter is when the brake fluid has absorbed 3.7% water, which takes about two years. In effect, it lowers the boiling point and thus reduces efficiency. The following numbers are minimums in order to comply with the stated category:
- DOT 3 has a boiling point of 401°F and a degraded boiling point of 284°F.
- DOT 4 has a boiling point of 446°F and a degraded boiling point of 310°F.
- DOT 5 has a boiling point of 500°F and a degraded boiling point of 356°F. (DOT 5.1 is the same.)
DOT 3 remains the great all-rounder, but other formulations can take higher temperatures. Some modern antilock braking (ABS) systems get very hot, so DOT 3 isn’t always recommended. The same goes for racing vehicles. Often, but not always, these use DOT 4. (Note that some manufacturers’ DOT 3 specifications are higher. If you’re regularly making long trips with lots of braking, or you like to take your classic car to track days, these are a good idea.)
DOT 5 is silicone-based, so it doesn’t absorb water and can take higher temperatures as a result. It also doesn’t degrade as quickly. However, it does foam and can create air bubbles, which reduce effectiveness. Most vehicle manufacturers don’t recommend it, so it’s largely used in military vehicles. The fact that it doesn’t absorb water means it won’t corrode braking systems if the vehicle sits unused for long periods.
DOT 5.1 is chemically similar to DOT 4, and it can be mixed with it. It’s not silicon-based, but it performs like DOT 5. However, at many times the price of DOT 3, it isn’t popular, and in most cases, it doesn’t offer sufficient benefits to be worth the extra money.
Did You Know?
Mixing DOT 3 and DOT 4 brake fluid won’t cause a problem if you usually use DOT 3. However, if DOT 4 is recommended for your vehicle, you would be lowering the boiling point, and there’s a chance the performance could suffer as a result.
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Features
You want to buy DOT 3 brake fluid because that’s what the manufacturer says to put in your car or truck, but which one? To be fair, there are a lot of similarities, and it isn’t easy to choose between them. The good news is it’s pretty hard to go wrong as long as you follow a few precautions.
Lubricant
Most modern DOT 3 brake fluids use synthetic lubricants rather than traditional mineral oil, but there are exceptions (some Rolls-Royce models, for example). Wherever possible, use what the manufacturer recommends, and don’t be tempted to use DOT 4 because you think it might improve performance. Some vehicles (typically Australian, but also Asian) use a different form of rubber than American manufacturers, and a few brake fluid formulations can attack the compound. Not a good idea! Mostly you’ll be fine, but you don’t want yours to be the exception, so double-check.
Brand
Although it’s important to choose the right type of DOT 3 brake fluid, that doesn’t mean you’re restricted to the original equipment manufacturer, such as Toyota, Ford, Honda, or Chrysler. Although the difference might not be huge, these are often a few dollars more expensive, and products from the major lubricant brands are as good or better.
SAE rating
You may also see an SAE rating (typically J1703), which means it conforms to or exceeds the standards set by the International Society of Automotive Engineers as well as the DOT.
Compatibility
Check that the brake fluid is compatible with your braking system: drums, discs, or ABS. Most work fine with the first two but not always with the latter.
Service life
Service life is often quoted as two years, but it is three for some brands. That means it’s probably more resilient to the effects of water absorption and doesn’t break down as quickly.
Caution
DOT 3 brake fluids contain harmful chemicals. Keep the containers away from kids and pets. If you’re doing the fluid change yourself, keep them away from the work area until you’re done and cleaned up.
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Accessories
Brake fluid bleeder: ARES Brake Fluid Pressure Bleeder
It’s vital that there are no leaks and that the pressure is constant throughout your braking system. In auto shops, they use a compressor-powered tool, but these aren’t cheap. This affordable manual pump is ideal for the home mechanic. It works on disc or drum brakes and makes it an easy one-person job.
Hand protection: Gloveworks Heavy-Duty Gloves
If DOT 3 brake fluid can eat through auto paint, imagine what it can do to your hands. Nitrile offers better protection than latex against oils and solvents, and these gloves are extra thick for better tear and puncture resistance. They also have a textured surface for a secure grip on your tools.
DOT 3 brake fluid prices
When we put together a product review, we usually like to give an indication of budget, mid-range, and expensive options. With DOT 3 brake fluids, there isn’t really enough variety for us to do that.
If you buy a cheap DOT 3 brake fluid, you can get a gallon for around $20. You’ll pay $15 to $25 for a quart from a premium brand, but most vehicles only need a quart. In two years’ time, the cheap gallon stuff will have degraded — all brake fluids do — so it’s a false economy.
The bottom line is to make sure it’s the right type of brake fluid for your vehicle and buy the best. The difference isn’t enough to buy you a pizza!
Did You Know?
Most brake fluids are hygroscopic — they absorb moisture from the air. That’s not something you want, so regular checking of the brake fluid level should be done by looking at the side of the see-through reservoir, not by removing the cap.
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Tips
If you buy a pre-owned vehicle, there’s a good chance you won’t know when the brake fluid was last changed. If it’s a car you’ve had for years, maybe you don’t remember whether it was done last year or the year before. Here are a few indicators that a change is due:
- Check the reservoir. If your ABS brake warning light comes on, check the reservoir. It’s translucent with MAX and MIN levels. You should see fluid between these two marks, if it’s low, it needs topping up.
- Check the color of the fluid. You should open the reservoir as infrequently as possible because you don’t want to introduce moisture, but it’s okay to do it occasionally, like if the level is low. While you’re there, check the color. Most are yellowish, some are purple, but it should be fairly clear. If it’s muddy or has bits of debris in it, it’s time to flush out the old and add some new.
- Check the firmness of the brake pedal. Your brake pedal action should be progressive but firm and come to a definite stop. Sometimes a stiff pedal is an indicator, but usually, it’s the opposite. If it feels mushy — like you’re pressing on a sponge — the hydraulic system isn’t working as efficiently as it should. At a minimum, the brakes need bleeding to make sure there are no air pockets, but changing the fluid is a good idea.
- Check for puddles or stains under the car. Puddles or stains underneath a vehicle are never a good sign. You need to identify whether it’s gas, transmission fluid, or brake fluid and get it fixed ASAP!
FAQ
Q. How often should my brake fluid be changed?
A. Unfortunately, there’s no one answer. It depends on the vehicle and the maker. Some manufacturers say every 20,000 miles, others every 40,000 miles. Some say two years, some three, and some just say “periodically”! The only safe course is to go with the period set down in your owner’s manual. If you can’t find the information, go for the shorter period: every two years. Brake fluid isn’t expensive, and it’s better to be safe than sorry.
Q. Should I change the brake fluid when I change the brake pads?
A. It’s not absolutely necessary — you could just top up your brake fluid reservoir and bleed the brakes to get rid of any air — but it’s the perfect opportunity while you’ve got the car in the air and the wheels off. It will also make sure your whole braking system is in prime condition.
Q. How do I dispose of old brake fluid?
A. One recommendation is to pour it into a tray of kitty litter, let it evaporate, and then throw out the residue. We strongly disagree with that method. Brake fluid contains dangerous chemicals (including heavy metals) that should never go into ordinary trash or where there’s any chance of it getting into drains or waterways. Many auto parts stores will take it (in a separate container from other vehicle fluids), or you can contact your local waste authority for hazardous waste recycling locations.
