Hacker News Reader

Note that, for emmesions, heating up the car in stationary is actually positive. It prevents driving a car with a cold engine. Cold engines cause horrible inefficiency in cars. It's one of the reasons why city driving is worse for mileage and emissions than highway driving. Shorter trips.

View on HN

I am unable to find a source for this. Until now I thought heating up stationary is bad concerning all possible aspects, including emissions.

Seems to be caused by the period before the catalytic converter gets up to normal exhaust temperature.

“Vehicles fitted with catalytic converters emit most of their total pollution during the first five minutes of engine operation; for example, before the catalytic converter has warmed up sufficiently to be fully effective.”

https://en.m.wikipedia.org/wiki/Catalytic_converter

Sure. But otoh the car is idling for tens of minutes maybe and possibly no single part of the engine and exhaust system is gaining the needed temperatures to operate cleanly. This means more emissions, more wear and more stressed out neighbours. I'm sure about the last one at least.

There is probably a sweet spot. Certainly, you want to avoid loading a cold engine too much. But don't idle for qn hour either.

But then you cause those bad emissions in your car park while it's heating up :)

I don't there is a big benefit overall.

Reply on news.ycombinator.com