Brake Fluid Question

[kevinday]

I need to top up my brake fluid, the car is new to me so I do not know what type is in it. The cap says use Dot 4 fluid only. The only fluid I can find locally is Dot 5.1. Is it OK to mix, or should I flush through and replace all the fluid? I intend to have this done anyway on the next service, can it wait?

[lanciachris]

Dot 4 and 5 should NOT be mixed. you can get away with completely replacing all the fluid.

http://auto.howstuffworks.com/question451.htm

[kevinday]

Many thanks Chris.

[supaspark]

You can replace dot 4 fluid with dot 5.1 but you may have problems with seals later (check with dealer or manufacturer) ideally keep with dot 4.

[pesty]

Guys I think you may be getting mixed up here with dot 5 and dot 5.1.

As far as I know Dot 3,4 and 5.1 can be mixed and are compatable. Although it is probablybetter to bleed teh whole system

Dot 5 is different to 5.1. I am willing to be corrected but dot 5 is racing fluid and dot 5.1 is just a evolution of dot 4. the same as dot 4 was an evolution of dot 3.

YOU must not mix dot 5 with dot 5.1or 3/4

please feel free to disagree but if you look at any old car it will say use dot 3 only on the resovoir but you can use dot 4 etc etc.

Have I got it wrong?

Kevin,

In my head this makes sense the reason you can only find DOT 5.1 is because this has replaced DOT 4.

I am pretty sure if you read the back of the bottle of DOT 5.1 it will tell you if its compatible or not


>> Edited by pesty on Sunday 10th April 16:55

[supaspark]

pesty said:

Guys I think you may be getting mixed up here with dot 5 and dot 5.1. As far as I know Dot 3,4 and 5.1 can be mixed and are compatable. Although it is probablybetter to bleed teh whole system Dot 5 is different to 5.1. I am willing to be corrected but dot 5 is racing fluid and dot 5.1 is just a evolution of dot 4. the same as dot 4 was an evolution of dot 3. YOU must not mix dot 5 with dot 5.1or 3/4 please feel free to disagree but if you look at any old car it will say use dot 3 only on the resovoir but you can use dot 4 etc etc. Have I got it wrong? Kevin, In my head this makes sense the reason you can only find DOT 5.1 is because this has replaced DOT 4. I am pretty sure if you read the back of the bottle of DOT 5.1 it will tell you if its compatible or not >> Edited by pesty on Sunday 10th April 16:55

Your quite right dot 3 4 and 5.1 can all be mixed. Dot 5 is silicone based and may affect seals!!!!

[edc]

DOT5.1 has not replaced DOT4. DOT5.1 is the glycol equivalent spec of DOT5. IIRC Super DOT4 is the same as DOT5.1

[kevinday]

Errr.... The 5.1 is on the shelf in the petrol station, unfortunately it is all written in Hungarian and does not mention DOT 4 at all. IIRC I used DOT 5 in my 240Z Samuri, this was racing fluid and changed at least every year.

I am trying to get the car booked in for a total fluids change in the next week or two, however the brake fluid is a bit low, the warning light comes on at certain angles. It looks like a top up with 5.1 will be OK followed by a complete change to 5.1 when the car goes in?

[edc]

Pretty much all factors, dealer service centres will have some DOT4. You can use 5.1 if you want but it costs more.

[grahambell]

DOT 5.1 is compatible with standard DOT 3 and DOT 4 fluids so can be mixed. Has higher boiling point and only costs slightly more so using it to replace standard fluid is cheap easy brake upgrade for fast road use.