it does work but do not expect a miracle.
You may regain 1 or 2 % in parasitic losses. Lets put that in perspective on a standard engine.
Thats 2 - 3 bhp
Worth doing on a championship such as stock hatch where the engines are the same and 1 or 2 bhp will get your nose in the first corner first, but the reality is you probably will not notice on a normal car.
The thing is that often in racing you have to chase the small numbers. I'll throw me as an example. My engine will hopefully push out around 170bhp. A dry sump can add around 2%, crank scraper plate 2%, electric water pump 1%, lets add this device 1%, lightweight crank pulley and camshaft pulleys 1%
Thats a potential gain of 11bhp which isnt that bad
Kev