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I'm sure the cited expert really is an expert, but this article fails miserably at conveying any cohesive understanding from them to you. It's full of conclusio

I'm sure the cited expert really is an expert, but this article fails miserably at conveying any cohesive understanding from them to you. It's full of conclusions that don't follow from their leading statements. My understanding about warming up an engine before putting load on it had nothing to do with fuel or power steering fluid, it was about thermal expansion of all the machined parts that suffer wear if they are run under load while they are loose-fitting from being cold. This is a thing even in summer and merely worse in winter. This article barely talks about this and doesn't say anything intelligible but just says "stress" from stepping on it right away. Maybe that issue also no longer exists on modern engines, but nothing in this article explains that. Mostly everything this says about why idling is supposedly bad, applies to operating the thing at all, idling or not. The conclusion would be "don't use your car at all in winter" Well, if you're going to use it at all, then you're already doing the damage, so you might as well be comfortable and have an easier time clearing the windows. The device only exists in the first place to serve you.

willnonya 4y ago
Absolutely. The risk of putting load on the engine before the moving parts and oil have reached operating temps is far greater than the threat of tiny amounts of gasoline washing residual oil from the cylinder walls or thinning the oil. The only risk described here applies to prolonged idling only and is a long term risk mitigated by reasonable elwarmuo and oil changes. The short term risk is the rotating assembly and value train is far more immediate. Fuel injection has convinced people that they can just jump in a cold car, fire it up and be fine. Doing so, especially in extreme cold is just incredibly damaging.
- nickff 4y ago
  I work in this industry (designing tools for automotive diagnostics), and have heard many arguments either way WRT warming up engines; I do not understand yours.
nickff 4y ago
I work on the repairs side of this industry (diagnostic tools), and have come to the conclusion that while the thermal expansion is an issue, it’s probably not the largest or most fundamental one. When an engine idles (with no load), it produces relatively little heat. Comparatively, an engine running faster, under load produces much more heat. The engine will warm up more quickly and less evenly when loaded, likely leading to thermal stress, and possible mismatched thermal expansion. On the other hand, modern lubricants are very good at handling different temperatures. The other thing to consider is that the engine is only one part of the vehicle, and various other components of the drivetrain may actually suffer more thermal stress from the idling than from immediate driving.
- Gibbon1 4y ago
  > On the other hand, modern lubricants are very good at handling different temperatures. I think this is the key difference between now and what used to be. Also suspect modern engines are more carefully designed to handle thermal expansion.
MadScott 4y ago
Oil pressure seems to be left out of the conversation - oil-starved journal bearings can be bad news if loaded immediately. SOP in piston-engine aircraft is to get the oil temperature and pressure "in the green" before doing run-ups. There's a pretty good description here: https://www.machinerylubrication.com/Read/779/journal-bearing-lubrication https://www.machinerylubrication.com/Read/779/journal-bearin...
- bombcar 4y ago
  Some vehicles have oil heaters to get the oil to operating temperature before even cranking. These engines are often large enough to park a car inside, however.
  - willis936 4y ago
    My 2018 car (gasoline, turbocharged, direct injection) has coolant and oil temp readouts. The increase in coolant temp from a cold start leads the oil temp by a few minutes (exact time is dependent on ambient temperature and load profile). Once the oil temp starts to get above 150F it very quickly gets to the operating temp (220F), so I view that as the point that it's okay to go above 3000 RPM. If there are oil heaters then they must be far away from the oil reservoir temperature sensor and only have a local effect. As you say, that sounds like a feature for very large engines. It's probably a good practice to be gentle to car engines with cold oil.
    - bluedino 4y ago
      Most engines will have a lower redline until the engine has reached a certain temp
    - winrid 4y ago
      Street cars have been using coolant/oil heat exchangers to bring oil up to temp faster and regulate its temperature under load since at least 1999 (source: VW's 1.8T, AEB and AWP motors). https://store.ngpracing.com/acm-oil-cooler-heat-exchanger-1-8t-2-0-8v-1-9-tdi-audi-vw-late-model.html https://store.ngpracing.com/acm-oil-cooler-heat-exchanger-1-...
jimmaswell 4y ago
Anecdotally, my transmission doesn't shift as well if I drive it right away in the cold.
- mikrotikker 4y ago
  Yea on cold mornings I have to skip 2nd gear and go straight to 3rd, since I can't get into 2nd gear the first few times.
  - gonzo 4y ago
    synthetics work wonders
  - Gordonjcp 4y ago
    You should change your gearbox oil.
avereveard 4y ago
I have the same recommendation on my car user manual, don't warm the engine, but take off after start up and take it slow for a few minutes until the engine water moves off the base. I know one of the engineers that worked at the car design and when questioned, he explained (going off memory here) that people used to warm the engine, then started driving normally, and while the engine is hot, the trasmission and differentials aren't, but you don't have a good way of warming them up while standing still, so drive off slowly and carefully without asking full torque from your engine, and it will help warm the whole thing.
- Brian_K_White 4y ago
  Thank you. This makes sense.
- jonwest 4y ago
  Yeah, from my understanding, basically try to keep the engine load light until at least you’ve warmed your coolant to operating temperature, but ideally 5-10 minutes beyond that as your oil(s) will take longer to heat as they’re more viscous than coolant. Basically, drive like a grandma for ~10-20 minutes before even moderately giving it the business. The flip side of this is that, especially if you’ve got direct port fuel injection, you’ll actually want to give it the business on occasion (once properly warmed up) for best operation, as the detergent from an increased fuel spray can help to break up carbon buildup on the top of your pistons. Either way you’ll likely want to book in carbon cleanup as a periodic maintenance item.
  - givemeethekeys 4y ago
    Thats asking for a lot, considering my entire commute is 10 minutes, but I hit the highway 1 minute in.
    - jonwest 4y ago
      Honestly, the other commenter hit the nail on the head in that "optimum" doesn't mean "necessary"—but 10 minutes of a commute isn't enough to get your engine fully up to working temperature and you are shortening its lifespan. Maybe it doesn't matter to you, and that's totally fine. If you're changing vehicles every couple of years you're probably not even going to run into needing significant repairs as a result of it, but if you're planning on keeping your vehicles for a longer period of time it's definitely something you should consider.
upsidesinclude 4y ago
Modern vehicles have high quality oils, tight tolerances but rpm dependent oil pumps. At idle, the oil pressure is lowest, the fuel energy is lowest and consequently the engine will take the longest to come up to operating temperature. FYI
P5fRxh5kUvp2th 4y ago
I thought it was just me because I'm not an expert on engines, but apparently not. And I agree with your last point, it was the other thing that was bothering me by it. What exactly is actionable here, to me it's just normal wear and tear.

willnonya 4y ago

Absolutely. The risk of putting load on the engine before the moving parts and oil have reached operating temps is far greater than the threat of tiny amounts of gasoline washing residual oil from the cylinder walls or thinning the oil. The only risk described here applies to prolonged idling only and is a long term risk mitigated by reasonable elwarmuo and oil changes. The short term risk is the rotating assembly and value train is far more immediate. Fuel injection has convinced people that they can just jump in a cold car, fire it up and be fine. Doing so, especially in extreme cold is just incredibly damaging.

nickff 4y ago
I work in this industry (designing tools for automotive diagnostics), and have heard many arguments either way WRT warming up engines; I do not understand yours.

nickff 4y ago

I work on the repairs side of this industry (diagnostic tools), and have come to the conclusion that while the thermal expansion is an issue, it’s probably not the largest or most fundamental one. When an engine idles (with no load), it produces relatively little heat. Comparatively, an engine running faster, under load produces much more heat. The engine will warm up more quickly and less evenly when loaded, likely leading to thermal stress, and possible mismatched thermal expansion. On the other hand, modern lubricants are very good at handling different temperatures. The other thing to consider is that the engine is only one part of the vehicle, and various other components of the drivetrain may actually suffer more thermal stress from the idling than from immediate driving.

Gibbon1 4y ago
> On the other hand, modern lubricants are very good at handling different temperatures. I think this is the key difference between now and what used to be. Also suspect modern engines are more carefully designed to handle thermal expansion.

MadScott 4y ago

Oil pressure seems to be left out of the conversation - oil-starved journal bearings can be bad news if loaded immediately. SOP in piston-engine aircraft is to get the oil temperature and pressure "in the green" before doing run-ups. There's a pretty good description here: https://www.machinerylubrication.com/Read/779/journal-bearing-lubrication https://www.machinerylubrication.com/Read/779/journal-bearin...

bombcar 4y ago
Some vehicles have oil heaters to get the oil to operating temperature before even cranking. These engines are often large enough to park a car inside, however.
- willis936 4y ago
  My 2018 car (gasoline, turbocharged, direct injection) has coolant and oil temp readouts. The increase in coolant temp from a cold start leads the oil temp by a few minutes (exact time is dependent on ambient temperature and load profile). Once the oil temp starts to get above 150F it very quickly gets to the operating temp (220F), so I view that as the point that it's okay to go above 3000 RPM. If there are oil heaters then they must be far away from the oil reservoir temperature sensor and only have a local effect. As you say, that sounds like a feature for very large engines. It's probably a good practice to be gentle to car engines with cold oil.
  - bluedino 4y ago
    Most engines will have a lower redline until the engine has reached a certain temp
  - winrid 4y ago
    Street cars have been using coolant/oil heat exchangers to bring oil up to temp faster and regulate its temperature under load since at least 1999 (source: VW's 1.8T, AEB and AWP motors). https://store.ngpracing.com/acm-oil-cooler-heat-exchanger-1-8t-2-0-8v-1-9-tdi-audi-vw-late-model.html https://store.ngpracing.com/acm-oil-cooler-heat-exchanger-1-...

jimmaswell 4y ago

Anecdotally, my transmission doesn't shift as well if I drive it right away in the cold.

mikrotikker 4y ago
Yea on cold mornings I have to skip 2nd gear and go straight to 3rd, since I can't get into 2nd gear the first few times.
- gonzo 4y ago
  synthetics work wonders
- Gordonjcp 4y ago
  You should change your gearbox oil.

avereveard 4y ago

I have the same recommendation on my car user manual, don't warm the engine, but take off after start up and take it slow for a few minutes until the engine water moves off the base. I know one of the engineers that worked at the car design and when questioned, he explained (going off memory here) that people used to warm the engine, then started driving normally, and while the engine is hot, the trasmission and differentials aren't, but you don't have a good way of warming them up while standing still, so drive off slowly and carefully without asking full torque from your engine, and it will help warm the whole thing.

Brian_K_White 4y ago
Thank you. This makes sense.
jonwest 4y ago
Yeah, from my understanding, basically try to keep the engine load light until at least you’ve warmed your coolant to operating temperature, but ideally 5-10 minutes beyond that as your oil(s) will take longer to heat as they’re more viscous than coolant. Basically, drive like a grandma for ~10-20 minutes before even moderately giving it the business. The flip side of this is that, especially if you’ve got direct port fuel injection, you’ll actually want to give it the business on occasion (once properly warmed up) for best operation, as the detergent from an increased fuel spray can help to break up carbon buildup on the top of your pistons. Either way you’ll likely want to book in carbon cleanup as a periodic maintenance item.
- givemeethekeys 4y ago
  Thats asking for a lot, considering my entire commute is 10 minutes, but I hit the highway 1 minute in.
  - jonwest 4y ago
    Honestly, the other commenter hit the nail on the head in that "optimum" doesn't mean "necessary"—but 10 minutes of a commute isn't enough to get your engine fully up to working temperature and you are shortening its lifespan. Maybe it doesn't matter to you, and that's totally fine. If you're changing vehicles every couple of years you're probably not even going to run into needing significant repairs as a result of it, but if you're planning on keeping your vehicles for a longer period of time it's definitely something you should consider.

upsidesinclude 4y ago

Modern vehicles have high quality oils, tight tolerances but rpm dependent oil pumps. At idle, the oil pressure is lowest, the fuel energy is lowest and consequently the engine will take the longest to come up to operating temperature. FYI

P5fRxh5kUvp2th 4y ago

I thought it was just me because I'm not an expert on engines, but apparently not. And I agree with your last point, it was the other thing that was bothering me by it. What exactly is actionable here, to me it's just normal wear and tear.