I've been using in my souped up waterboxer and it works great. Anecdotally, I
drove thru the desert southwest last summer in 115 deg heat in my 2.3 L WBX
Syncro Westy with the AC on, and it never came close to overheating even on
long grades. I also used it in my previous hi-mileage stock WBX syncro. It kept
the motor noticeably cooler on long grades. If you don't use it with
antifreeze, it offers NO antifreeze properties, but does prevent corrosion. You can run
it with half antifreeze too, just not as dramatic cooling difference - but
still noticeable. That's how I run mine.
I won't run my van without it anymore. It's a proven product.
2cents
Chris Dixon