How long can a car idle?

Answer 1

I think it is safe to expect that just about any car can idle for at least 1 day per tank of fuel. Keep in mind that if you are planning only on idling your car, you can cause damage due to buildups in the cylinders, fuel injectors, and exhaust systems if the engine isn't revved periodically. Keep in mind that your car will idle considerable longer if it is left in park or neutral instead of "drive", and if you turn off the air conditioning, headlights, radio, etc..

Also, if you idle the engine excessively, you must visually inspect your oil, because you will need to change it more than every 3,000 miles.

The answer depends on the fuel efficiency of your car, Whether the car is in Neutral, or drive, and the appliances (AC, radio, lights, etc) you have on. As an example, my car gets 27 MPG on the freeway going about 60 MPH. My gas tank is 18 gallons. This means that on the freeway, my car would run for about 8.1 hours. This is because 18 gal per Tank * 27 MPG = 486 Miles per Tank and 486 Miles per Tank / 60 MPH = 8.1 hours per tank.

Keep in mind though that this only applies to my car, and it doesn't apply at idle, only at 60 MPH.

When you are moving, the car is burning fuel to overcome forces such as air resistance, and rolling resistance in the tires and wheels. When the car is idling the car is burning up just enough fuel to keep the engine spinning at the lowest speed that it can run, and to run the systems that are always on, such as power steering, the brake system, battery charging, coolant system. (all of the forces overcome at idle are insignificant compared with drag and rolling resistance while moving). I would guess that my car (1991 Ford Thunderbird) can idle for at least 40 hours. In real world experience, I left my car running for two hours with an inverter plugged in to serve as a generator, and I couldn't even notice a difference on the fuel gauge.