ive ben told that setting your heater on def makes it warm up faster on a cold day. is it true?

 

No.

Steve

 

Remember friction causes heat, so really the quickest way to heat up is to drive.

 

The fastest setting for heat is FLOOR. VENT is almost the same, but blowing higher (from the dash) will cause more wind chill. All the other settings (including DEF) cause the A/C compressor to run, which will cool before the heat comes up.

For the absolute fastest heating, unplug the compressor clutch & set the controls for MAX A/C & full hot.

 

it will warm up faster without the heater on. B.c the heater core is a small heat exchange (like a radiator) and you are robbing the engine of its heat until its warmed up, and has plenty to spare