Water can be injected into fault zones to trigger earthquake as was done accidentally
in the Denver Colorado swarm of the mid-1960s, and later in experiments near
Rangely Colorado. Some of these triggered earthquakes were in the upper magnitude
5 range and did damage to infrastructure in Denver before it was discovered what was
happening and the water injection was halted.
When reservoirs are filled with water, some of this water seeps into surrounding
faults and it is thought that this is at least partially responsible for reservoir-induced
seismicity (along with loading from the water itself). These earthquakes can also
be large enought to do significant damage - Like Oroville, CA or Koyna, India - both
in the Ms 6+ range.
Oily or greasy substance might be able to lubricate the fault, but they have little
corrosive ability. Water actually dissolves some of the rock in the fault zone
by corroding it and putting it into solution this opens up the places where faults
are locked and allows slippage. Greasy or oily substances do not have the
hydrogen bonding of water and would not be anywhere near as good at doing
this.
For the most useful triggering, choose water.