1994 Cadillac DeVille Owner's Manual - Page 219

Run your engine only as long as you must. This saves fuel.When you run the engine, make it go alittle faster thanjust idle. That is, pushthe you accelerator slightly. This uses less fuel the heat that get and it for keeps the battery charged. You will need a well-chargedbattery to restart the vehicle, and possibly for signaling later onwith your headlights. Let the heater run for awhile. Then, shut the engine off and close the window almost allthe way to preserve the heat. Start theengine again and repeat this only when you feel really uncomfortable from the cold. But do it as little as possible. Preserve the fuel as long as you can. To help keep warm, you can get out 206