The Amsoil stuff appears similar to the ELC coolant being used in heavy trucks now. If it is... it would be hard to beat. The ELC stuff is supposed to go for 600,000 miles in a semi truck engine. Though not a real issue for most gasoline engines, ELC handles cavitation on cylinder walls better than the reds or greens of earlier years. Like ELC, the Amsoil stuff seems based on Organic Acid Technology. The ELC stuff is far cheaper to buy though. I recently flushed and filled my semi. It came with ELC and I stayed with that. I got a 50/50 mix of ELC at Love's truck stops for about $10 a bottle. Would most likely be cheaper at a traditional retail outlet, but most other outlets didn't have anything like it. Most still had the old red that required SCA's. The ELC stuff is maintenance free... no need to test and recharge SCA's. It has a better heat transfer rating than the traditional red stuff as well.
The Technology and Maintenance Council that set the standards for truck specifications in the industry is recommending going to ELC for all engines. So... propylene glycol, or at least the Organic Acid Technology style, must not be a bad thing, and heat transfer is not an issue. Especially when it is now being used frequently in heavy trucks that are regularly pulling gross vehicle weights of 80,000 lb, even in mountains, like mine. I went with the same stuff in my Jeep Liberty Diesel. It is wet sleeved just like my Cummins.