part of your question- no the block heater will not make your car run any warmer or colder once it reaches operating temperature. it certainly will ease cold starting and the car should warm up faster. if the temp. only reached 40 to less than 80 deg on the dash gauge you need to replace the thermostat. it's not good for the engine to run so cool no matter what the season.

bob in ct

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1984 300D Turbo - 231k....totalled 11/30/07 RIP