Morris Minor Owners Club

Hi used shell dot4 I have half litre carlube dot4 synthetic. Same stuff? Or do i need to use mineral based. Is the shell stuff probably synthetic?

Doesn't it say on the bottle? I know DOT5 silicone fluid says it's compatible with dot4 fluid.

Unless it's special stuff for Rolls-Royce or Citroen then I would have thought it's OK.

DOT5 silicon is definitely NOT compatible with DOT4!

But yes it is ok to mix the Carlube DOT4 with the Shell DOT4. No need for mineral based fluid.

Neil MG wrote:DOT5 silicon is definitely NOT compatible with DOT4!

But yes it is ok to mix the Carlube DOT4 with the Shell DOT4. No need for mineral based fluid.

Anything mineral is NOT compatible with british car braking systems (or most others too!) and will wreck the seals.

Neil MG wrote:DOT5 silicon is definitely NOT compatible with DOT4!

Where do you get that from?

It says on the bottle that DOT5 silicone can be mixed with DOT4 and I've done it with no problems whatsoever.

Stig28 wrote:

Neil MG wrote:DOT5 silicon is definitely NOT compatible with DOT4!

Where do you get that from?

It says on the bottle that DOT5 silicone can be mixed with DOT4 and I've done it with no problems whatsoever.

Just poor a little of each into a glass jar and see! Give it a shake!

What exactly does it say on the bottle? Most probably it says that DOT5 is compatible with DOT3/4 brake systems, (not DOT3/4 fluid.)

I was under the impression that silicon would mix with dot4, but negated the advantages of the silicon. Will have to check on that now!

Concur with les.

Just for the record Silicon fluid WILL NOT mix with DOT 4. They are NOT compatible. Before switching from one to the other the system needs to be completely flushed and ideally all seals and hoses changed!

There is a lot of debate over which is best silicon or DOT 4 and I could not hope to ever find agreement there. I am in the silicon camp because it doesn't damage paint and doesn't need to be changed every two years. But I also respect that some people have had problems and would never use it.

There should be no debate about compatibility! Again I would say for an immediate evidence of this just mix a little of each in a container. Give it a good shake or stir and watch the two fluids emulsify and then settle.

My advice to anyone who has mixed fluids is to drain and flush the system, change the seals and hoses and refill with one or the other.

I didn't say they'd mix, they're different densities so they don't. That doesn't mean they're not compatible. After all, water does mix rather well with glycol fluid but that doesn't mean it's a good idea to put it in your braking system!

OK we can agree to differ, but I would recommend that anyone who is thinking of mixing or thinks that the two fluids may be compatible to at least do a bit of research (start with google!) before proceeding.

my dad put silicon in his MO but that was when we replaced all cylinders and lines

Charles are you going to brooklands?

No I am on call for work unfortunately