Cars: fuel consumption at idle?

I have close engineering familiarity with heavy-duty diesel engines. A 15-liter diesel engine can idle on about a gallon of fuel per hour, which means a big-rig with 150 gallons of fuel on board could idle for six days non-stop.

What’s the story for cars? If I have a 3-liter V6 engine and a 16-gallon tank full of gasoline, how long can I idle before I’m out of fuel?

A typical car burns somewhere between 0.1 and 0.2 gallons of fuel per hour at idle. Your v6 will probably be on the high side of that, probably around 1.7 or 1.8.

At 0.2 gallons per hour, your 16 gallon tank would be emptied in 80 hours, or a bit over 3 days.

You mean 0.17 or 0.18?

Uh, yeah.


My bro has a 2003-ish Altima with an inline 4 cyl. Which he left running in a parking lot with a mostly full tank of gas. Three days later when he returned it was out of fuel. :smack:

So ballpark, less than 3 days. :slight_smile:

You have to tell the rest of that story.

I’m picturing something like the taxi in the movie Airplane, which still has the passenger sitting in it and the meter running at the end of the movie.

Not that exciting. The car is one of those with the remote fob thing with no actual key and there’s a push-button on the dash for engine start & stop. He leaves his fob in his pants pocket while driving.

Bro is a pilot like I am. Drives to the airport employee parking lot at 0-stupid-thirty in the AM. As he’s parking he gets a phone call from the scheduling department. IOW, his *de facto *supervisor of the moment. “Are you late? When are you going to get to the airplane? Yada yada yada.”

So he’s got a phone in one hand as he’s climbing out of car, grabbing his gear from the trunk, pulling on his jacket, and rushing to catch the employee bus that’s passing by. If he misses that bus it’s 15 minutes standing out in the cold and there went time to buy breakfast (=Egg McMuffin) before starting work. Plus earning another panicky phone call from the already-testy scheduler.

Somehow in the rush and distraction he never pushed the engine stop button. Like all modern cars it idles real smoothly, doesn’t make much noise, & has non-stinky exhaust. So he never noticed anything was amiss. Pushed the lock button on the fob & got on the bus.

Three days later he comes back from the trip and rides the bus to his car.

The car cranks just fine but won’t light off. Won’t even fart. How often do you have hard-starting problems on modern cars? Almost never. Eventually he notices the gas gauge pegged below E. His first thought was somebody stole his gas despite the locking gas port door. Then he remembers the flail getting out of the car.

Oops. :smack: Once he got somebody to bring him a couple gallons it fired up immediately.