Just wondering if anybody knows if Fabia Vrs shock absorbers are oil or gas filled?

They are gas mate.

What's the gunk that leaks out when they start failing?

What's the gunk that leaks out when they start failing?

erm, liquid gas???

Not sure myself but I always thought the dampers were oil damped. I know when my KWs started failing, they were leaking a gunky black oily residue. Of course KWs are not stock fabia dampers (if only!)

They are gas pressurised, but still oil filled, so by the time the oil starts leaking out, all of the gas has already gone!

Can't remember what the gas pressurisation does though I'm afraid.

Gas dampers still contain oil, the main difference is gas dampers always self level.

Here is an explanation of why shocks are gas pressurised.

Gas-pressurized shock absorbers

It is to make the performance more consistant.

I think that you need load levelling shock absorbers for them to self level, which is a different thing again.