Hmm. That's an interesting thought. I'm not sure the seals inside would like being in oil full time, even though pneumatic systems like that typically have oil injection somehow. Plus I'm sure you'd have to dial the hyd. pressure way down to not blow things apart. But I don't see why with a possible seal upgrade and keeping careful eye on pressures it wouldn't work. Likely be a bit cheaper, no? More common I would think, just because air is speedy and time is money...