I have this unit and so far I am very impressed. Here are my notes on it:
-Suction is generated using an internal venturi and muffled exhaust.
-130psi sustained will net you 25"hg vacuum
-110psi sustained will net you 20"hg vacuum
-90psi sustained will net you 15-20"hg vacuum
-Air line adapter, replace it with a ball shut-off valve that has a standard air hose ball/swivel nipple (Lowes Sells both items for $5.00). This way you can connect your air supply using a standard fitting and and turn it on when needed. Otherwise the internal venturi will flow air anytime the air hose is connected. The unit comes with an odd coupler, it was the first thing I replaced and if memory serves me correctly it did not require any reducers or adapters meaning teflon tape + connector is all that was requried.
-The unit has an internal check valve that preserves the stored vacuum in the tank! I love this feature!
-VERY LARGE capacity, I can change the oil in the Mercedes (8.5 liters twice) and the VW once without emptying the tank!
-Excellent for extracting transmission fluid from the O1m!
-The unit comes with multiple rods and hoses. Don't get hung up on the plastic quality, the hoses are all easily replaced if you need a specific diameter for your car. They are simple compression fitting adapters so it's a 30 second swap out.
-Adapters are Steel and brass using o-rings to maintain the seal with the main suction hose, this provides a completely clean and mess free extraction of oil. The only issue I found is the hoses get really hot when extracting oil. Oil must be at operating temp to work optimally and maximize removal of the engines old oil...drainage to the lowest point etc. The unit will suction out cold oil BUT it is much slower and will require a lot of air (read noise)
-Suction hose, has a ball valve that allows you to stop the flow and recover the vacuum in the tank.
-Air compressor, The system works best with high pressure high volume. The venturi is metered, meaning it has a small orifice that reduces the volume of air required to make the unit work. This lowers the required capacity (CFM output of your compressor) so that most 4-6CFM @90 psi units will do the job. If you can maintain 130+ the suction level improves greatly and reduces your total time for extraction of the fluids.
-Noise, the unit has an exhaust muffler, so the nose is cut down and is best described as a moderate level continual "whooosshhhhh".
-Site gauge, you are able to read the volume of oil in the tank using a clear tube that shows the fluid level. eliminates the guess work when extracting large sump volumes.
-Other uses, Lawnmower, air compressors, transmissions, motorcycles etc.
Compared to a Pela, this thing knocks it out of the park. No pumping, no mess, no fuss! Also the tank is EXTREMELY easy to drain.