Here's a good summary. They used it on an older IDI diesel, so it may only help w/ lower injection pressures and/or with vehicles that have a well worn FI system. Stuff like this has been around for decades IIRC, and was can be used to reduce the
viscosity of crude and some of it's refined byproducts. That said there are some
valid apprehensions regarding this device, and if it is a scam I think that the testers were smart to use a Benz instead of something w/ a rotary pump like a VW diesel where dynamic timing (as well as efficiency) depends on fuel viscosity.