Submitted by giuliomagnifico t3_yk2sm8 in science
I’m guessing that’s subzero in Celsius, not Fahrenheit. Big difference between the two and how it affects vehicles.
In freezing conditions an electric block heater would help quite a bit. A diesel without a block heater may not start at all if it’s cold enough.
And 30 minutes of preheating is ridiculous. 5-10 minutes is enough to get the fluids warmed up.
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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Gas cars will also not start given sufficient cold
While they do become harder to start, most modern gas cars will start in extreme cold weather (Below -40c/f) without block heaters, so long as the battery is in good condition.
Diesel vehicles suffer more because of the incredibly high compression that the starter has to overcome, in addition to the environmental factors that effect both vehicles the same.
In my youth, I lived in the far north of Canada and I remember having to put an insulated tarp over the front of the truck and running a tiger torch under the truck for 15 minutes to get things warmed up. You did this if the truck cranked but didn’t fire. You didn’t want to grind down the battery too much. We couldn’t plug the truck’s block heater in while on the ice road, off the grid. It worked like a charm. Craziest part was when you disconnected the torch from the propane tank, I remember seeing liquid droplets of propane flow out onto the ice before boiling off in the frigid air.
Managed to successfully start my car in -73F weather when I was in high school. Thankfully the cold snap only lasted a couple of weeks.
Car had a battery pad and battery blanket, oil pan heater, and a heating/circulation pump. These days I use a trickle charger in place of a battery blanket or battery pad.
-73F! Where were you if you don’t mind me asking. Canada? Does that include windchill? It got down to -35F during the polar vortex in 2019, but it was considered pretty dangerous and we were all told to remain indoors, whole city got off work and everything.
Interior Alaska. There was zero wind. We were suffering from an inversion at the time so all of the moisture from the vehicle exhaust and wood smoke from wood stoves was collecting in the valley as ice fog, and it was so dense you could barely see to drive (plus it reflected headlights back at you worse than regular fog).
They didn’t close schools due to the temperature, but only closed them because of the number of bus accidents occurring on the roads due to poor visibility because of the ice fog. I don’t know if things have changed, but they didn’t even have a provision for closing schools at the time because of the temperature.
Oh wow. Yeah I know what you mean about the temperature causing school closures, it’s common now but it didn’t used to be a thing. That’s crazy though! Especially if people had had to go outside after those accidents. -70F puts you at extreme danger of frostbite within minutes (although perhaps less so if zero wind? Not sure, just my guess).
Yes that has to include the windchill unless they are in alaska or northern Canada. I live in northern Canada and the coldest I have seen is -50c without the wind
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-50F is such an extreme you pretty much need to leave it running.
That is…literally true, but it’s practically not an issue for most people with well-maintained vehicles.
I’ve started every vehicle I’ve ever had, one with over 200k miles it (with a good battery),in sub-zero Fahrenheit at least once without issue. The oldest was a Subaru with the short piston skirt design, so it made an awful lot of noise, but there was never an issue actually starting.
It'll likely start, but it if the coolant is all frozen solid......
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5-10 minutes of gently DRIVING will get the fluids warmed up. There is no need to idle to warm a vehicle up in most cases. Besides, the only real way to warm up some parts of the drive train is to drive. The only practical benefit is for the driver’s comfort.
The cab also needs to be warm enough to prevent the windows from fogging/icing up.
True. Definitely a consideration I wasn’t thinking about. In my climate it’s usually very dry during very cold days, so fog isn’t an issue. Even on moister, warmer days the defrost setting will still pump out dry air and keep the windshield clear. It’s COLD, dry air, but the cold doesn’t bother me.
You’re right, though. If I turn on the defroster setting and the windshield doesn’t clear up I’m forced to wait.
This can be mitigated with proper cleaning.
The engine has to warm up. And driving isn’t the best way to do that. Oil gets very thick in really cold temps and doesn’t lubricate properly. Your car might start and run but your probably doing damage to you engine.
The best way to warm up an engine is while under gentle load.
Even if you don’t use top-tier boutique synthetics, any modern API-rated oil will properly lubricate the engine for the vast majority of us. If you live somewhere really cold, where it gets we’ll below zero Fahrenheit, an easy solution is to use a full synthetic, meaning at least a good Group 3 oil, 0W-XX oil.
An oil’s pour point isn’t a great indicator of whether an oil will pump adequately upon startup, but it does show you that even a decent synthetic like Mobil 1 10W-XX oil will still pour at -39C. They offer other synthetics that are down in the -50s C.
Sitting there idling your engine to warmup also prolongs the time it takes for the oil’s viscosity to reach the point where wear is minimized. Regardless, at the temperature most of us experience during the winter (positive degrees Fahrenheit), the wear on your engine will likely not matter in a practical sense. Lubrication IS happening. The thought that you’re running your cold engine dry for some period of time is simply not true.
Anecdote: we get into the negative teens Fahrenheit for at least a few days each winter where I am most winters. Even still, my oil pressure light goes out nearly as quickly as when it’s warm out. The oil pump does have a bypass, which will open when the oil is very cold and thick; however, the pump is positive displacement and an adequate amount of oil will pump to the supply channels almost instantly. That’s. It even to mention the leftover film of oil and boundary layer of additive protection left on the bearing surfaces.
Ok you start your engine at -40 then drive it instantly and see how long you engine last. While your driving your running at a much higher RPM then idling. All that extra wear will cause premature engine issues. You do what ever you want. I will continue to warm up my engine before I put them under load.
You’re talking things way out of context and exaggerating the risk. Much higher RPM? Most cars cold idle at 2K RPM as is. I’m advocating driving off gently, not starting up at low temps and gunning it immediately onto the highway. Besides, I’d argue that overloading an excessively cold engine is more likely to result in catastrophic failure such as a cracked head, blown gasket or spun bearing. Who cares about wear at that point?
Also, did I even mention doing this at negative 40? I was pretty clearly stating that most of us start and drive our vehicles at temperatures at which the oil is immediately properly lubricating the engine, far from the limit of the oil. On the flip side, just as your example of loading up an engine at negative 40 is absurd, so to is warming up your engine by idling at, say, 0C.
Most of us, including me, never even see close to -40 where I am. As mentioned, I RARELY see below zero and never below the negative teens Fahrenheit, which I think is pretty common. Under these circumstances, starting up and driving off gently is the best thing to do.
As mentioned before, the only way to warm up the rest of the drivetrain is by driving. I think that’s neglected, and some who warm up their engines have no problem loading up the rest of their bone-cold drivetrain. If you do idle your engine to warm it up, I hope you at least still drive gently for a bit to warm up the rest of the car.
I get it, though, it’s human nature to want to take care of things that are so important to us and cost so much money. But, just because you think your engine is as cold, brittle and sensitive as you feel doesn’t make it actually so.
Finally, I don’t begrudge anyone who wants to warm their car up for personal comfort. I think it’s wasteful and polluting, but we all do things in our lives that pollute and we can improve on, so who am I to give someone a hard time. If the conversation comes up, however, I will make it known that warming up an engine for the engine’s sake before taking off is all for their peace of mind only the majority of the time.
Who warms their vehicle up when it isn’t negative temps? That is a complete waste of time and gas. Well where I live it gets to minus 40 every year and averages around -20 all winter. That’s what warming up an engine means to me, not at plus 2. So yes I guess your right at the temps your talking about it’s fine to drive to warm up your vehicle but not in the winters where I live.
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it depends on how cold and wet it is tbh, if it's freezing outside and there's ice all over every window I'll probably let it warm for 10-15 minutes minimum so it's easier to scrape off all the ice. If there's no ice on the car I don't care though, I'll just let it warm for 3-5 min if it's extremely cold or just get up and go if it's only moderately cold
Good point. The only time I idle to warm up is while clearing ice and snow off the car. The heater may not put out a ton of heat, but the rear defroster (and front in my vehicles) will get the melting started while I work on the rest of the vehicle.
> subzero in Celsius
Of course!
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The block heater in a diesel heats the coolant in the engine block, which in turn keeps the oil and fuel in the engine warm, but it does nothing for the fuel in the tank. Anywhere that gets a real winter switches the type of diesel you get at the pump for the winter season so that gelling is not a concern.
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Maybe in some trucks, probably semis. DEF tanks in modern consumer trucks are heated too, but not by the block heater, and that stuff will freeze solid if it's cold enough. In your typical 2500-3500 series pickup the fuel in the tank will be heated when the truck is running, but by hot fuel recirculating from the return line, not an electric heater. If we're talking about plugging in your average normal person diesel car or truck, the only thing being heated is the block. Some people add additional heating pads to things like the battery, and oil and trans pans. I've never heard of anyone putting a pad on a fuel tank.
Often not . You google it
I swapped the tank in my diesel Grand Cherokee, there absolutely wasn't a heater in it. It wasn't super happy about it but it started at -35°C.
"But it's still cold in the car after a few minutes, I need to be toasty for my 10 minute drive."
Heh, people in my neck of the woods don't care about the fluids, they care about the inside temp of the car...
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>I’m guessing that’s subzero in Celsius
Check the source.
So, last winter I left my car outside overnight & then idling for 25minutes in -35°C, it was not warmed up even then & was not safe to drive.
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Ya try driving in -38F weather only letting your car warm up for 5 to 10 minutes. Its so cold my fluids never really thaw out.
I did it at least a few times a year when I lived in Fargo, ND. Just drive easy until the engine is warmer. The engine warms up faster when you're driving than it does idling in the driveway.
And is hard on your engine. It’s not being lubricated properly. You’re doing damage to your motor.
A lot of what I've read says it's harder on your engine to idle when it's cold than to drive easy. In part because the lubrication gets spread around sooner.
Edit: And let's make sure we're talking about the same thing. I'm talking start your engine, and then start driving normally within 30-60 seconds, vs starting your engine and letting it idle for 10-20 minutes.
>most modern cars are able to successfully circulate oil within 20-30 seconds
Not when it’s cold. Oil doesn’t pump properly when it’s thick. Even when your driving easy your RPM are still well above idle RPM. I don’t know where you’re reading that from but as a mechanic I can assure you that it’s wrong. With the oil technology further advancing it getting better but it’s still hard on engines.
You'll have to forgive me if I believe the experts at the car manufacturers, Liqui Moly, Shell, and Esso over a random "mechanic" on Reddit.
From Consumer Reports:
>Modern cars have improved on technology to the point that your engine is fully lubricated within 20 to 30 seconds. By the time you get in, start the car, put on your seatbelt, and get situated, the engine might not be fully warm, but it’s completely lubricated and you’re okay to drive at this point.
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-38F is an extreme situation. At 0F 5-10 min is enough.
At -38F I might not shut it off at all.
-38f is not really an extreme situation its just winter.
The fluids may be “warm” but you also need to wait for the engine block to heat up. Metal contracts when it’s cold and forms a tighter grip around the pistons causing excessive wear in the cylinders if you don’t let the engine block get nice and warm.
Block heaters for the cold are the best option.
The pistons contract, too. The combustion will also act in the piston and piston rings pretty much evenly, tending to center the piston in the cylinder. The layer of oil the piston rings ride on in the cylinder cross-hatch will also mitigate wear, even at low temps. The main concern might be that the piston contracts more than the cylinder, so some additional fuel dilution and bypass may occur, requiring a more-frequent oil change in the winter.
Also, the longer the engine is maintains at reduced temperatures the more wear there will be. Idling to warm an engine up takes a lot longer than gently driving off. While driving at low loads, I would argue that you’re actually reducing wear compared to excessively idling to warm up all the time.
Practically speaking, driving off gently soon after starting the engine is the second best option. The first is an external source of heat, which is the point of the article, if I’m not mistaken.
I've read a few books on taking care of older cars, though I imagine the same holds for modern vehicles. They all say, all things being equal, it is better to put the engine under light load than to run it stand still to warm up.
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