Jsancho007

Hello everyone,

I haven't purchased my car with fuel efficiency as the primary goal, but I've noticed something interesting. My car is equipped with an onboard computer, and I regularly check the average fuel consumption, especially since I acquired it five months ago.

Typically, I start the engine from cold and allow it to run for a short while to raise the oil temperature slightly. However, I've noticed that fuel consumption increases when the engine is idle. This seems counterintuitive to me.

I would expect fuel consumption to be higher when driving at 3-4k rpm, but it's actually the opposite. When I let the engine idle, consumption rises, but it gradually decreases when I'm cruising.

I'm simply curious about this phenomenon!

Thank you

centerpunch

What units does it use for fuel consumption?

Obviously, if the car is not moving it is getting zero miles per gallon.

sacman

It's working as the mileage isn't increasing during idle.

Jsancho007

that makes sense !!

Thanks

Jsancho007

Europeans usually use litres per 100km

pp000830

Hi J,
The root cause may be that the computer is calculating fuel consumption per mile, if the car is standing still the consumption per mile is infinitely large and so the average consumption per mile on a display will begin to climb at idle.
Also, a contributing factor may be increased fuel consumption when the engine is started from dead cold at idle and the ECU may be setting the mixture to be a little rich to encourage smooth idling until the engine warms up.
Andy