Hi just to throw my two bobs worth in i have a set of the cooler thermostats in my truck here in Australia (thanks for that Kat !) i live in tropical Queensland and my main reason for fitting was to keep the under bonnet temp down cooler air into the engine ! I have worked for the CAT dealers in Australia for years and asked the question years ago why do CAT engines need to run so hot well the answer I got was because of the sulfur in the fuel was the reason causing engine component wear valve guides especially every body here in Oz with a turbo ford six (petrol) runs cooler thermostats for the reason of cooler air temp into the engine more power Also the purpose of the thermostat is to REGULATE temperature and create a restriction in the block to allow the coolant to absorb heat to be carried to the radiator
thanks guys