This does work! I have yet to try it on the HCH II because it has to be installed in front of the radiator which you have to take apart some of the plastic moldeing to get to. I have tried it before on other vehicles and it does help. It takes a little less time for the the vehicle to warm up and it will produce heat faster in the cabin. I do not recomend leaving it a year round, especially if you live in a hot weather climate as it will increase your engine's core temp. when in the summer you want to lower the temp.