Crap I never noticed that. It is too damn hot over here in Okinawa, same latitude as Miami. That cramped engine room with twin turbos sitting in traffic going 20mph stop and go for an hour or more. Many people I know don't run a thermostat for that reason. Coolant is definately important unless you are only running a 1/4 mi and shutting her down. I believe Turbonetics has a page on their web site about the benefits of watercooling. Plus, they sell both water and non-water cooled turbo's, they should know. I would definately trust Turbonetics over Greddy or Mitsubishi (who makes the TDO series turbos). Z from Japan