How Often Should Brake Fluid Be Changed? A UK Driver's Guide
Written by Petro Olekhnovych, mobile mechanic in Aylesham, Kent
As a general guide, the RAC says brake fluid should be changed every two years or every 24,000 miles, whichever comes first. The right interval varies by car, so always check your handbook or service book for your model’s schedule. Brake fluid wears out even if the level looks fine, which is why it has a time limit and not just a mileage one.
How often to change brake fluid: the short answer
The RAC’s guidance is every two years or 24,000 miles. It also says the interval can vary with:
- The make and model of the car.
- The quality of the fluid used.
- Your driving style.
The RAC adds that some owners may need a change every year at their MOT or service. Your owner’s manual gives the type of fluid your car needs and how often to replace it. If you have lost the handbook, your service book or the car’s service history should show when it was last done.
Why brake fluid needs changing
Brake fluid is the hydraulic liquid that carries the force from your foot to the brakes at each wheel. The RAC explains that it also lubricates the system and helps prevent corrosion. On many cars, the clutch uses it too.
It absorbs moisture
The problem is that brake fluid absorbs moisture from the air over time. According to the RAC, this reduces how well it works and how well it protects against corrosion. Carwow notes that damp or humid conditions can speed this up.
Moisture lowers its boiling point
Braking creates a lot of heat, for example on a long downhill stretch. The RAC says brake fluid is designed to have a high boiling point for this reason. Carwow explains that absorbed moisture lowers that boiling point, which can lead to a spongy pedal or weaker braking.
Old fluid can damage other parts
The RAC warns that if brake fluid is left too long, other braking parts may be damaged. That can be far more expensive to put right than a fluid change.
Need a service or brakes doing?
Servicing, pads, discs and fluids done on your driveway across East Kent.
WhatsApp for a free quote Call 07563 350335
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
Signs your brake fluid may need changing
You cannot rely on how the car feels, because old fluid can seem fine in everyday driving. Carwow lists these warning signs:
- A soft or spongy brake pedal.
- Reduced braking performance or longer stopping distances.
- Dark or dirty fluid. Healthy fluid is clear or light amber.
- Brakes that feel inconsistent after repeated or heavy braking.
- Being overdue on the service interval, even with no other symptoms.
A spongy pedal can also mean air in the system or a leak, so it always needs checking. Our guide to a spongy brake pedal explains the causes and when to stop driving.
If the brake warning light comes on, or you think fluid is leaking, stop driving and get the car checked. Without enough fluid, the brakes cannot work properly.
How to check your brake fluid level
You can check the level yourself with the car parked on level ground. The DVSA’s driving test guidance is simple: find the reservoir under the bonnet and check the level against the high and low markings.
- If the level sits between the marks, that is a good sign, but it does not tell you the fluid’s age or condition.
- If it is below the low mark, do not just top up and forget it. The AA says a drop in level is a good indicator of a leak, so it should be checked.
- Look at the colour if you can see it. Carwow says dark or dirty fluid is a sign it needs changing.
Only ever use the type of fluid named in your handbook. Carwow lists DOT 3, DOT 4 and DOT 5.1 as common types and warns that using the wrong fluid or mixing types can reduce braking performance and may damage seals.
Does the MOT check brake fluid?
Only in a limited way. The MOT inspection manual says level checks are limited to transparent reservoirs or where an indicator is fitted. A level below the minimum mark is a minor defect, significantly below is major, and fluid not visible at all is dangerous.
The tester can also fail contaminated fluid, but only if they can clearly see it. The manual admits that on many vehicles you will not be able to see this. So passing the MOT does not mean your brake fluid is fresh. Keeping to your service schedule is what matters, and our car service checklist explains what a proper service covers.
How we can help
We are a mobile mechanic based in Aylesham and we come to your home or workplace across Canterbury, Dover, Deal, Sandwich, Folkestone and the villages in between. See the areas we cover.
- Servicing at your door. We carry out interim and full services, so your car’s service schedule can be kept up to date without a trip to a garage.
- Brake checks and fault finding. If your pedal feels soft or a warning light is on, we can come out, find the cause and tell you what it needs.
- Brake pads and discs. We replace pads and discs on site.
- Clear pricing. Labour is £30-£50 per hour depending on the job. Parts are extra, and we agree the price on WhatsApp before any work starts.
Frequently asked questions
Does brake fluid go off if I hardly drive?
Yes. It absorbs moisture from the air over time, which is why the RAC gives a time limit as well as a mileage limit.
Can I just top up old brake fluid?
Topping up restores the level but not the condition of the fluid already in the system. A low level should also be checked for the cause.
How is brake fluid changed?
The RAC describes draining old fluid, refilling and bleeding each brake circuit in the correct order. Some cars need diagnostic equipment for the ABS. The RAC says it should be done by a mechanic or garage.
Need help? Send a WhatsApp to 07563 350335 with your car’s make and model and we’ll come to you.
Need a service or brakes doing?
Message us on WhatsApp with your reg and postcode for a price before any work starts.
WhatsApp for a free quote Call 07563 350335
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
