Yay, tech papers!
Regular(Pink) Water Wetter:
http://www.redlineoil.com/content/files/tech/WaterWetter Tech Info.pdf
Diesel(Blue) Water Wetter:
http://www.redlineoil.com/content/files/tech/Diesel Water Wetter Tech Info.pdf
Although, I noticed, Redline says WW is now compatible with DexCool. The paper for regular WW is more fleshed out than the Diesel one, but it's basically that Diesel one doesn't have any anti-corrosion additives, is compatible with ELC additives, and so forth.
HD coolants do use different chemistries from automotive stuff. IIRC they use nitrates to break surface tension, to combat the hot spots and cavitation problems.
Soooo....
In race cars and track day cars, when you have to flush the coolant because anti-freeze is banned, and run water... Water Wetter helps.
For an every day DD type car, with a cooling system that is healthy and happy. Diesel type may help, but it probably won't do much.
For a modified ride, pushing the cooling system, and running antifreeze because you live where it may freeze... Well then the Diesel type may help more noticeably in that case.
The take away, OE coolants are specced to do a job, and to do a job for a price, the cheaper the better. Your everyday car probably will live a million miles with regular maintenance and some preventative care.
I run some heavily modded toys, I help take care of some very stock stuff, and I live where it can get to -40C, I've had anti-freeze turn slushy... Anyways, I run the Diesel version in my toys and some others as test cases, and I've not had coolant sludge. I've run the regular WW with deionized water in my desktop's water-cooling setup both Intel and AMD.
So, it works, but you have to pick the right product, and realize that when used in a system with a coolant mixture, the results are far less than when used in a pure water setup.
Edit:
I have to get a coolant drain and refill soon on my mom's Hyundai. I can see the oil temperature in the head as well as the ECT. I should do some back to back tests with Diesel WW, and record the coolant/temperatures with the outside temps. That would show in an automotive application if it's helping lower more than just the coolant temps. I can probably do it in a month or two from now. Same day, back to back runs on the highway.