DBLX

Has anyone noticed that while idling, with the mpg display up, that the mpg drops/declines... ? I was idling and noticed I was sitting at about 15.6 and it starting dropping... By the time i pulled off it was down to 14 and probably would have dropped lower. Does this seem right? I would think it would stay at 15.6 since the truck wasn't moving, just idling.
Any thoughts?

TIA,
DBLX

2000xl_toronto

makes sense because the truck is expending fuel but not moving at all. This is especially common if you've recently filled up because the mpg is cumulative so if you've filled up recently then there isn't very much data and the truck is saying I'm getting terrible gas mileage because I'm burning fuel and going nowhere

greggebhardt

It makes perfect sense.

2000xl describes it well!

DBLX

Ah, I see from that point of view.

NorCal-09

Yes, it does.

The computer is merely responding to the current data supplied.

Similar to this, if you are coming off of a long, steep, downgrade on the Interstate with little or no throttle input, and you reset the MPG readout, it will show 99 MPG, until you give it some gas, and then it will drop to say 75 or 68 MPG, until you get back on the flat again, and add pedal pressure, wherein it will resume a real-world reading.

big_ole_truck

Great explanation 2000xl

Thunderslide

it is easirer than that if your engine is running and you are not moving you are getting zero miles per gallon start adding zero's into any average it will drop.

cujet

Try turning your engine off and see what the average MPG display is. I think you will find the very same thing car manufacturers find. Idling for more than a few seconds wastes fuel.

I'll bet you can keep your MPG indication up by doing this. (what a PITA)

DBLX

I'm not really concerned about the wasted fuel while idling. I know that... I was surprised to learn the computer was still calculating mpg while idling in park. That seems crazy to me.

Quixoticelixer

that's one reason city mpg I'd lower than hwy.
that and having to get back up to speed.