Does Brake Fluid expire in a sealed tin? [Answered]


A2OC Donor
I will need some extra brake fluid (it was changed last year). I found I need Dot 4 for the0 A2. Prices vary on ebay and offline and some tins seem slightly corroded, so could be old. Does it life expire in an unopened tin?

I've seen

ebay - Audi VW SEAT Skoda Brake Fluid DOT4 Genuine B000750M1 - 500ml @ £16 . The photo sample shows a code 091018 which could be a date code
ebay - Genuine VWG Brakefluid DOT 4 250ml - 250ml @ £10. No code visible
Halfords - Mobil Brake Fluid DOT 4 - 500ml @£8. I'm sure that will be fresh but seems cheap even at the non offer price of £.
ebay - Brake Fluid DOT4 Dot 4 Plus 0.25Ltr Fits Ford Audi BMW VW Peugeot Febi 26748 - 250ml @ £7.60. No code visible

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It would appear on google that the shelf life of an unopened tin/bottle is infinite Alan although some give a shelf life of two to five years. If they are opened then best discarded after 12 months as the fluid absorbs water once exposed to air.
There’s a good blog about Brake Fluids on Demon Tweeks. Brake Fluids our Expert Guide.
Found it at

That was informative though unfortunately it did not answer my question. Key points:
  • Ratings such as DOT 3, DOT 4, DOT 5, and DOT 5.1 are among the most widely used in the automotive industry
  • DOT 5.1 has strict viscosity standards at lower temperatures in addition to having a high boiling point.
  • in cold climate areas, the DOT 5.1 brake fluid is very commonly used on most modern cars.
  • The most widely distributed brake fluid is the DOT 4.
  • The boiling point temperatures of DOT4 is very similar to those of DOT5.1
  • The major difference is the viscosity at low temperatures.
  • Today, cars are commonly equipped with ABS, and DOT5.1 fluid is used since the viscosity of it helps the ABS work consistently even in very cold climates.
  • Brake fluids with a rating of DOT 3, 4 and 5.1 are all Glycol based fluids and, as such, can be used in the same braking system.
  • DOT 5 brake fluid is silicone based and is not compatible with any of the other types of fluid.
    • As such, it is best to switch and use this fluid only when you have had a complete braking system overhaul
    • including new hoses, as any traces of other brake fluids will be detrimental to braking performance.
Article goes on to recommend "Best Racing Brake Fluid" brands.

I did a google search and found the answer to my question "does brake fluid expire?" at
  • If you have a sealed bottle of brake fluid that has never been opened, your brake fluid has an infinite shelf life.
  • An opened bottle is different, having a shelf life of about a year.
Still, I think I will avoid very old looking stock with rusty tins!

Edit: Another article is more cautious
  • Actually, as long as it remains unopened, you have little or no reason to fret regarding whether it will go bad or not since it is claimed by most of its manufacturers that it does not have an expiry date.
  • Be that as it may, you are not advised to store it for upwards of two years, at the most, even if its container has not been breached.
    • [because the seal may deteriorate]
  • An opened bottle will absorb moisture over time, which is detrimental to its effectiveness.
  • After a year, toss it.
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Looks like you can't go wrong with Mobil from Halfords if you have a Halfords near by.

I use Pagid 5.1 in my A2.
Just looked at the Halfords' site again. The Mobil has increased slightly in price (dynamic pricing to make the indecisive buy?) but also noted:
  • Mobil Brake Fluid DOT 4 ESP 500ml at £9.49 (normally £12).
Says it is formulated for cars with ESP.
To be honest I’ve never thought too hard about brake fluid, I use the most recent dot but only use 5.0 on my mountain bike.
I buy in 5lt tubs so I keep it for some time. I have always thought that it can only absorb the moisture in the air in the tub so I minimise the number of times the top comes off. When doing a brake job I decant into an old large tea pot and get the top back on the tub.
I know I have had A2 brake problems but keeping and using fluid the way I do is not the cause. My A2 is the only car I have owned that has had caliper issues.
I’d forgotten about EPS, it works very well. Once had a blow out at 70. A2 ran straight and pulled over safely. I’m not aware that it needs specially formulated fluid.
Just looked at the Halfords' site again. The Mobil has increased slightly in price (dynamic pricing to make the indecisive buy?) but also noted:
  • Mobil Brake Fluid DOT 4 ESP 500ml at £9.49 (normally £12).
Says it is formulated for cars with ESP.
Formulated for cars with ESP?
Marketing flim flam.
The brake element of ESP is ABS. ABS has been around for a while now, I don't think it's ever been suggested that it requires specific brake fluid ...
A differentiator. Give it a few months, and they all will be "formulated for cars with ESP"
Then none of them 🤔
Yeh, I did think it was marketing hype. Just like toothpaste with a scientific sounding extra ingredient that is supposed to harden or whiten ones teeth against everything at twice the price. I avoid but my OH gets taken in :(