1994 GMC Suburban Owner's Manual - Page 74

To use the engine coolant heater, first turn off the engine. Theii oqpenthe hood, unwrap the electrical cord and plug it in. It uses normal house voltage ( I 10 volts), but: A CAUTION: Plugging the cord into an ungrounded outlet could causean electrical shock.Also, the wrong kind of extension cord could overheat and cause a fire. You could be seriously injured. Plug the cord into a properly grounded three-prong 110-volt outlet. If the cord won't reach, use a heavy-duty three-prong extension cord rated for at least 15 amps. I NOTICE: After you've used the coolant heater, besure to store the cord in the manner it was, to help keep away from moving engine it parts. If you don't, it could be torn and damaged. How long should you keep the coolant heater plugged in? The answer depends on the weather, the kind of oil you have, and some other things. Follow this chart. Engine Coolant Heater Usage Viscosity/ Oil Grade SAE I OW-30 SAE 15W-40 32°F to 0°F (0°C to -18°C) Not Required Not Required 0°F to -10°F (-18°C to -23°C) Two Hours* Two Hours:$ Below -10°F Below -23°C Eight Hours* or Overnight Eight Hours* or Overnight "The times listed are minimum times. It will not harm either the coolant heater or the vehicle to leave the coolant heater plugged in longer than the times stated. For best results in cold weather, use Number 1-D diesel fuel or a "winterized" Nutnber 2-D fuel. 2-18