Carb heat simply raises the temperature of the air entering the intake of the engine. Running full carb heat when the ambient temperature is low will not harm your engine in a measurable manner any more than running your engine in 115 degree heat in Arizona. It will reduce the amount of power your engine can produce and will marginally raise the operating temperature of the oil and engine temp but it will not hurt anything. The IO360 comes in a turbocharged version and think about the temperature of the intake air after it runs through a turbo which is spun by exhaust gasses. A little heat extracted off the exhaust header is relatively speaking, cool.