I'm sure nobody here still idles their engines to warm them up. Aside from being a colossal waste of fuel, it does nothing to warm the other critical parts of the drivetrain that affect fuel economy: the tires, transmission oil, bearings, differential, etc.
So I did a mini experiment to chart the relationship between coolant temp, intake air temp (warm air intake in place) and fuel consumption in Litres per hour according to the ScanGauge.
The test conditions:
- ambient: -7 C / 19 F
- cold soak (hadn't driven it since the day before)
- all electrical accessories off
- WAI in place
- didn't touch the accelerator at all - let the engine computer do its thing
Observations:
One of the most astonishing things I saw was how
long it took the little motor to warm up. Holy crud:
17 minutes!!
I heard back from a Metro driver on the Canadian prairies (not Peakster) who told me his Metro actually starts to
cool down from normal operating temperatures at stop lights on really cold mornings with the cabin heat running.
Anyway here's the chart I was after: