Submitted by giuliomagnifico t3_yk2sm8 in science
Reply to comment by dr_xenon in 30 minutes of car preheating in sub-zero conditions produces as much particulate emissions as driving 97km in a gasoline car, or 20km in a diesel car “These findings do not suggest to stop preheating cars; instead, we could reduce the emissions by using similar methods that are in place for engine” by giuliomagnifico
Umm, there are parts of the US that regularly go subzero too. In Farenheit.
Yes but the title is most likely refering to metric because they used km. Also 0°F is not a very important specific temperature, while 0°C is a very important temperature.
> while 0°C is a very important temperature.
Only for water. Cars use antifreeze which, by itself, freezes at 0°F, but mixed properly with water it freezes at -40° (F or C).
I was refering to the concept of "subzero", which is used a lot in metric countries, but I can't imagine it being that useful in you operate in F.
Wasn't refering to the relevance of 0°C to vehicles.
"Subzero" temperatures are common in the northern US.
That... Doesnt matter?
"Sub zero" is a reference in C. Just because you can aply to any referencial that goes bellow 0 it doesnt really matter.
But, we say "subfreezing." Your meteorologist likes to say sub zero in the US because he's a cool MK character. There's really no other reason.
I don't care what your car has inside it. 2/3rds of the rock it rolls on is water. Problems will arrise if you drop below the freezing point of water, for your car, your home, your health...
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> Only for water.
Not just for water. Subzero Celsius means rain turns into snow, and also that windscreens start freezing, thus requiring pre-heating to de-ice it.
>Not just for water. Subzero Celsius means rain turns into snow, and also that windscreens start freezing, thus requiring pre-heating to de-ice it.
That's because rain and snow are... water.
Not arguing that his comment fighting over 0C being important only for water isn't silly because there's a lot more water in your car than just coolant (vapor, ice, snow, etc affect more than just driving conditions), but pointing out rain vs snow is still just talking about water.
Of course.
But the comment I was replying to also mentionned to use “antifreeze” to avoid pre-heating, as if the problem with pre-heating was liquids.
It’s not.
The problem is the snow, which starts at 0 Celsius.
I mean, that's fine. The way you said it didn't make much logical sense to me.
I'd have told him that it's not about the engine's water freezing (or not), but rather about warming the engine to deal with the environmental effects of freezing water and general cold. Defrost the ice on the windows, stop fogging windows, and the fact that most humans aren't happy in freezing temperatures. Skip the part that reads like it's not about water freezing, but that it's about water freezing.
That's also not correct. It can sleet or snow significantly above 0⁰C. Hail pretty much ONLY occurs well above 0⁰C. The coldest day I've seen hail on was in the high 30s F, the warmest I've seen it was around 80⁰F.
In dry air, pooled water can start freezing around 40⁰F fairly easily. In REALLY dry air, drops can freeze way above that.
It depends on relative humidity as well as dry bulb temp.
Edit: is actually dropping a mixture of rain, sleet, and hail outside my window right now at 39⁰F.
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Was gonna say, but I also live in a weird part of the country (4-5hrs from the four corners). Today it was 12°F when I woke up, and in January it is rare for me to start the car when it’s over -10°F. My car is very heat efficient so it takes longer but 10mins is fine, my shifter will wake up soon enough.
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