I have an '00 E250 with the 5.4 gasoline motor that parts on a slight incline, nose pointing downhill that idles maybe 20-30 minutes in the cold winter mornings here in Ohio. Oil changed religiously every 3K miles but is this harmful to the engine? It does have about 241K miles and due for replacement in the next year and the new motor would also be idled as well.

Thanks for any advice or input!

 

No. Today's fuel injected engines run lean enough that it doesn't really hurt anything but gas mileage.