No wonder many car makers are putting in an engine shutdown when idle feature. So far the winter here has been kinda mild.
Idling wastes fuel!
Myth Busted: Idling wastes fuel! | Green Action Centre
How does Toyota counter this comment?
I’m surprised that nobody has raised the issue of the oil sump- that’s where gravity drains the engine oil down to when the motor is not running. Hot oil can take several minutes to drain back down into the sump once the engine is stopped, but the process begins the moment the engine is stopped.
Every time you start an engine, there are inadequately-lubricated metal components that wear against each other until the oil from the sump circulates enough to adequately lubricate the engine. This process takes less than a minute, typically, during which much wear is done to the engine- metal can rub against metal, ejecting tiny metallic dust particulate all over your engine. This metal dust collects carbon deposits and makes your oil black instead of light brown. Also, the wearing-down of your engine components ruins the precise tolerances and can lead to “blow by”, stealing power and allowing hot cylinder gasses to escape into the oil and pollute it.
Also, the heat-cycle of stopping-and-starting an engine causes additional wear to rubber seals and plastic parts and other components prone to become brittle from heating-and-cooling cycles.
There’s always a thin coat of oil, even when a vehicle sits for many days. Otherwise you’d hear obvious grinding. Do a test on a piece of metal and let it sit at various angles. It will remain slimy. Piston rings trap a bead of oil above them, also. There’s enough oil (when the engine is already warm) to protect from significant friction during restarts. That’s why start/stop systems on hybrids avoid damaging engines. Those are also being introduced on some non-hybrids. Cold starts cause most of the actual wear but it’s generally subtle if one does it right. No cold revving!
More total wear is caused by idling itself, especially on cold starts when the rest of the drive-train isn’t warmed up in sync with the engine by moderate driving.