What clutch fluid can I use? It says girling castrol...

[greenmeanie]

If it comes in a blue box that usually means it is Britpart. In this case it brings up the option that it doesn't matter what fluid you use as it will be leaking within a month anyway. Some of their stuff isn't bad but beware rubber from a blue box.

[amcordo]

If it comes in a blue box that usually means it is Britpart. In this case it brings up the option that it doesn't matter what fluid you use as it will be leaking within a month anyway. Some of their stuff isn't bad but beware rubber from a blue box.

I had a new Proline MC that I used off the shelf stuff from Autozone - rubber dissolved to the point of failure in about 5 months. Even if you can use anything just avoid the risk and order a couple of gallons of Castrol GTLMA online and keep it around the garage. No reason to risk failure on any of the parts!

[Apis Mellifera]

It is my understanding that the original hydraulic seals were made of a form of (natural?) rubber that would break down if exposed to anything other than Castrol GTLMA type fluid (DOT 4). Silicone (DOT 5) can also be used, but cannot be mixed with any other fluids.

However, it appears (from the experience of people on this forum) that the seals of current manufacture allow the use of other fluids without any ill effects.

That said, I stick with Castrol GTLMA because I can: it seems to be easy to get around here.

Corrections to my comments on fluids are welcomed.

That's basically it. Seals were at one time, when the trucks were new and the manuals written, natural rubber and thus would dissolve if the incorrect fluid was used. Natural rubber is now expensive as compared to synthetic and no longer used (for other reasons too). It doesn't matter what fluid you use. If you have a failure of a brake seal nowadays (assuming you're not still running 30 year old parts), no magic fluid would have prevented it.

[greenmeanie]

I had a new Proline MC that I used off the shelf stuff from Autozone - rubber dissolved to the point of failure in about 5 months. Even if you can use anything just avoid the risk and order a couple of gallons of Castrol GTLMA online and keep it around the garage. No reason to risk failure on any of the parts!

Apis nailed it. Its not the rubber compund reacting, its not the fluid. With the blue box its just really, really bad quality control.