When pressurized gas breaks through a seal at over 200 psig differential, perfectly good seal material can degrade....if it has insufficient physical properties. This is because gas is compressible and liquid is incompressible (much energy is released with the gas "escape"). We already know that leaks are way too prevalent, and our seal material hasn't proven to be anything to brag about. The top quality seal materials are expensive!
Just because some people have done it and gotten away with it doesn't mean everyone will. If you do not have a leak at 200 psig nitrogen (or air), you WON'T have a leak at 4000 psig oil. There is simply no need.
Use at your own risk, but the philosophy (of not using excessively high pressure gas in hydraulic system pressure testing service) comes from industrial experiences much more broad than the automotive repair industry.
Just because some people have done it and gotten away with it doesn't mean everyone will. If you do not have a leak at 200 psig nitrogen (or air), you WON'T have a leak at 4000 psig oil. There is simply no need.
Use at your own risk, but the philosophy (of not using excessively high pressure gas in hydraulic system pressure testing service) comes from industrial experiences much more broad than the automotive repair industry.