I see far too many people sit in their parked car with the engine running. According to some sources, that's not good for your engine. And I don't think you need to keep charging the battery if you leave the AC on for only 10 minutes or so. Am I missing anything? What's your opinion on this?

Here are some facts from the CA energy commission... (consumerenergycenter.org/myths/idling.html)

Myth #1: The engine should be warmed up before driving. Reality: Idling is not an effective way to warm up your vehicle, even in cold weather. The best way to do this is to drive the vehicle. With today's modern engines, you need no more than 30 seconds of idling on winter days before driving away.

Myth #2: Idling is good for your engine. Reality: Excessive idling can actually damage your engine components, including cylinders, spark plugs, and exhaust systems. Fuel is only partially combusted when idling because an engine does not operate at its peak temperature. This leads to the build up of fuel residues on cylinder walls that can damage engine components and increase fuel consumption.

Myth #3: Shutting off and restarting your vehicle is hard on the engine and uses more gas than if you leave it running. Reality: Frequent restarting has little impact on engine components like the battery and the starter motor. Component wear caused by restarting the engine is estimated to add $10 per year to the cost of driving, money that will likely be recovered several times over in fuel savings from reduced idling. The bottom line is that more than ten seconds of idling uses more fuel than restarting the engine.

 

YES.
But up here in NE Ohio we often have to get the windows cleared. I let the engine idle while I'm scraping the windows. That takes a minute or 3 but it's far from "warmed up". I won't drive away until I can see out the windows.

 

Right, that makes sense. I'm just curious about those cases where you park in the parking lot with the engine running for seemingly no reason. I wonder if they know something I don't.

 

"CA energy commission," is charged with reducing the amount of fuel used, not engine wear. This message speaks to their organizational purpose.

Several years ago, to be politically correct, FedEx / UPS told their drivers to shut off the engines every time they stopped
for a walk-up to the door delivery. Don't recall any subsequent message from these companies as to whether that
has saved or cost them money. Would be the only good source of data, imo.

Why don't you contact them? (a good posed question ... maybe worth a couple of phone calls?)

 

Well, but if you look at how Honda defines "severe driving" condition below, idling is listed as one factor. So, idling can't be good. If it is good, why...? That's what I'd like to know... Does restarting your car take as much fuel as it is to leave the car idle? (I don't think so) What other reasons are there?

• Driving less than 5 miles (8km) per trip or, in freezingtemperatures, driving less
• than 10 miles (16 km) per trip.
  
• Driving in hot [over 90° F(32° C) conditions.
  
• Extensive idling or long periods of stop-and-go driving.
  
• Driving with a roof-top carrier, or driving in mountainous conditions.
  
• Driving on muddy, dusty, orde-iced roads.

 

The severe schedule has idling in there because the engine is running and no miles are being added to the odometer. So a belt on a car that idles for an extended period of time has less miles, but more wear. The same thing with fluids like oil, coolant, etc...

I think that idling for longs period of time wastes fuel to run the engine, the cooling fans, etc... Extended idling will leave you with an engine that is really older than the odometer says.

I don't think idling hurts your engine any more than normal driving. The oil, ATF, coolant, etc is pumping through the engine at the proper pressure. The engine won't overheat as long as the cooling fans work properly.

 

Cooling fans don't switch on until the temperature is a bit higher than normal, but not so high that it matters. Oil pressure is lower, but then the loads on the main & rod bearings are lower too.

The weenies that have their remote start & leave the car running for 15 minutes before they brave the cold, well, that's just a waste of fuel.

There's always mitigating circumstances... I had to warm the car up when the kids were newborns, but that doesn't last forever. And certainly not when we weren't going to put them in the car.

Actually, I hate to have the car running when I'm not right there. Too many things can happen. Not just someone jumping in to steal the car. I've never had the oil pressure go bad on me, but I sure would've felt stupid if I wasn't in the car at the time.

 

Less biased than a bureaucratic government agency? An American Society of Mechanical Engineers study:

 

I bet that's a warm/hot restart. Not the same as starting a cold (20deg.F) engine. So that plot would be appropriate if you're talking about turning off the engine for 5 minutes when you go inside someplace.

You'd use a different set of data to talk about warming up a COLD engine like myth #1 in the first post.

 

Hoot, Hoot.
.006 gal of gas/min for idling a V-6 = $0.02/minute fuel cost for idling a V-6

two cents / minute = not my worry. thanks.