Why do you need the best brake fluid? Is there really that much difference between them? Surely if they meet the authorized standards, then they’re going to be the same, right? Will a ten dollar brake fluid perform as well as a $30 brake fluid?
I’ve found that there’s a lot of misinformation regarding brake fluids. So, for the purpose of this article, I’ll be leaving aside brake fluid that conforms to DOT 5 standards. The reason? It’s completely different and there’s really no need to run it in a road car.
Let’s run through some of the basic information first.
Essentially, a normal or fast road car will use brake fluid that conforms to a DOT 3 or DOT 4 standard. The only difference being at what temperature it boils. The lower the temperature the less useful it is for heavier or faster applications.
The temperature at which it boils is crucial to safety. If the fluid starts boiling, then you risk inducing a vapor into the system. This, of course, doesn’t have the same pressure behind it. You won’t be able to put pressure on the pads or shoes, therefore leading to inefficient braking.
We should also understand that many fluids have a ‘dry’ boiling temperature and a ‘wet’ boiling temperature. Brake fluid, by its very nature, is ‘hygroscopic’. That means it absorbs water from the environment. The more water it absorbs, the lower the boiling point, and the less pressure you can put in the system.
The dry boiling temperature will, of course, always be higher. The temp at which a completely unused, sealed (therefore with no moisture) fluid will boil. A wet temperature assumes a degree of moisture in the fluid. It will always be significantly lower than the dry temperature.
DOT 3 should have a minimum dry boiling temperature of 401 degrees Fahrenheit, DOT 4 should be 446 degrees Fahrenheit.
Why do you need to bleed your brakes?
Well, partly as we’ve already discussed, brake fluid will take on moisture from the atmosphere. Just like engine oil, it can also degrade over time. Some fluids have a habit of wearing brake seals. That could mean the fluid gets contaminated with tiny rubber particles – leading to brake problems.
The good news is that if you have some mechanical knowledge, ‘bleeding’ the brakes is relatively easy. This originally meant bleeding the air out of the system. However, now it really means anything to do with changing the fluid.
You used to be able to buy the brake fluid in a couple of different colors. It was handy to see when you’ve completely replaced the fluid. However, modern brake fluids are either clear or a light amber color. This makes it more difficult to see when you’ve completely refreshed the fluid.
But running the cylinder to near empty and pushing through new fluid a few times should ensure that the whole system is clean and fresh.
The easiest way to change the fluid is to have the vehicle off the floor on all four corners. 99% of the time you’ll need to remove the wheels. However, with some vehicles, it’s possible to bleed the brakes without doing that.
If you haven’t already, invest in some quality jack stands and a hydraulic floor jack. It really will make the process so much easier and quicker. If you’re a solo mechanic you’ll need some sort of automatic brake bleeder. Ideally, you’ll have a spare pair of hands (or feet) to help you out.
You should start at the wheel furthest away from the main master cylinder. Usually, the rear opposite to the driver. Open up the master cylinder and make sure there’s plenty of brake fluid in there. Then, slowly crack the bleed outlet on the brake. Next, use a hose and trail that into a jar with fluid in the bottom. That way you can see if there are any air bubbles coming out.
Once the line is clean, and there’s no air, lock it off and move to the next wheel. Repeat the process. Be sure to keep the cylinder topped up with fresh fluid though. If not, you’ll risk introducing air back into the system again.
It’s that simple.
One word of advice – try not to get any brake fluid on a painted surface, because it makes an effective paint remover!
QUICK TOP TIP:
If your vehicle has a noisy water pump, try a few drops of brake fluid in the cooling system. There’s a high chance that it’ll cure that noisy bearing within seconds.
The 7 Best Brake Fluid Reviewed
As I said, I’m ignoring DOT 5 brake fluid for this review, concentrating on DOT 3 and DOT 4 as they cover around 99% of the cars on the road now.
We’ve chosen seven different fluids. They all have their benefits. But, they’re pretty similar as long you get the right rating.
In no particular order.
I like the fact that this is available in smaller quantities – great for motorcycles or those that are just looking to top up their system.
Motul RBF600 is 100% synthetic (most brake fluids are now), and completely non-silicone. It has great thermal resistance and stability with an extremely high boiling point, both dry and wet – 594 degrees Fahrenheit dry.
If it remains sealed, there’s no worry of shelf life and will last for years, so buying a few bottles could work out for you – instead of buying one big bottle and leaving the rest to soak up the moisture. The downside to the Motul fluid is that it is quite heavy on the hygroscopic front, meaning that replacement is recommended around twice a year if you’re using the vehicle heavily.
A great product that will work in nearly everything apart from serious race cars.
Another large bottle, still competitively priced though, and it exceeds the DOT 3 standards by a margin – 494 degree Fahrenheit dry boil, but that does drop considerably when wet – 292 degrees. So if you’re happy replacing the brake fluid at a regular interval, this would work well for you.
Similar to the other brake fluids listed, it’s a blend of synthetic esters that give great anti-corrosion properties, blends with other fluids and is happy in most braking systems – ABS, discs, and drums.
This is a unique blend of polyethylene glycol ethers and additives to ensure it gives excellent anti-corrosion properties. It mixes well with other fluid and prevents the hardening or softening of brake seals.
It easily exceeds the minimum boiling point of DOT 3 ratings. It has a dry boiling point of 446 degrees Fahrenheit and a wet boiling point of 339 degrees F. it’s not quite as high as the Prestone when dry but easily outperforms it when wet. It’s also compatible with all rubber components and seals.
- Rating: 4.8 / 5
- Brand: ATE
ATE says there’s a minimal decrease in boiling temperatures from dry to wet, thanks to ‘water locking’ properties. I don’t know what these properties are, but the dry boiling temperature is 536 degrees F, and wet lowers that down to 374 degrees.
In fact that ATE suggests this DOT 4 racing brake fluid is possible to extend the life between fluid changes to up to 3 years. However, if I was using the vehicle heavily, I wouldn’t run that far. The chance of brake fade would be too high.
It’s non-foaming when filling and bleeding, which is very important and has extra additives to help with corrosion protection and avoid steam bubbles. Yep, it may be possible to run it for three years, but for the sake of a few dollars, I wouldn’t.
It comes in a 1-liter bottle, which is great if you’re intending on replenishing the whole system, but if you’re looking to top up and bleed the system, you may find you’re wasting a fair bit of that.
The blend of polyglycol ethers makes sure that hot braking systems won’t cause issues of vapor release. It’s designed to work in most braking systems as long as they rated at DOT 3 standards – that’s discs, drums and ABS safe.
The specifications exceed the minimum figures for DOT 3. Dry boiling happens at 460 degrees F, wet is 284 degrees. It’s aimed at regular cars; not for high-performance use. A comprehensive range of additives and inhibitors helps with the anti-corrosion properties, and overall, the Prestone fluid gives an excellent margin of safety for all braking conditions.
32 oz. is plenty, again if you’re looking for a complete replacement you’ll use it all. A perfect DOT 3 brake fluid product that offers value for money.
Perfect size for my liking. Interestingly, this Castrol 12509 brake fluid has been engineered to mix with most other braking fluids and systems, it mixes well with other brands.
It’s a unique formula, and offers outstanding performance in all high temperature, high load braking systems, giving optimum response and feel. I’ve used Castrol products for years, and they’ve never been below par, always giving great value and service.
If you’re looking for high-quality brake fluid, this has to be on the list.
I’ve seen brake fluids advertised this way before – like a combo of DOT 3 AND 4. But in my mind, it’s a pointless exercise – ALL DOT 4 fluids will exceed the DOT 3 rating, that’s just common sense.
They say it’s for on & off-road use (again, aren’t they all?) and that it’s an extreme race fluid. But, the fact of the matter is that it has a lower dry boiling point than the Motul RBF600, by some margin. However, it’s still pretty high – 470 degrees Fahrenheit.
Again, this also is been engineered to guard against vapor lock and build-up. It absorbs relatively little moisture from the atmosphere, which in theory gives it quite a long service life. It’s compatible with all systems and prevents seal softening and hardening.
Hopefully, you’ll see that some brake fluids cope better with longer service intervals. And some can offer higher boiling points, but usually at the price of more regular replacement. The key to it all is understanding what it is you need and want from your brake fluid.
While I’ve given a rough indication as to how easy changing the brake fluid can be, I’d have to say that if you have any doubts, then maybe you should seek professional help. After all, this is the brakes on your car that we’re talking about, and you really don’t want an issue with them.
Finally, be aware that the bleed outlets on a brake caliper can seize shut. Too much force on the wrench and you’ll just snap them off. That’ll give you a whole world of pain if you want to change the fluid. You’ll either need specialist equipment to try and remove the broken portion or a new brake caliper. Either way, it’s costly.