[British-cars] Castrol LMA Brake Fluid Question

[csx2282]

I've been unable to find a local source for Castro's LMA DOT 4 brake fluid,
but have found their synthetic version which is supposedly DOT 3 and DOT 4
compatible.  However, I leery mixing this stuff with the old glycol based
Castrol DOT 4 fluid.  So my question is have any of you mixed these two
versions of Castrol brake fluids?  Anyone feel there might be a concern with
doing so?  If it's not considered a good idea, I guess I'll scrounge around
for some other DOT 4 brand.

Thanks,

Roland