4 ms·

Two reasons this is bad: 1. Emissions, catalytic converters and such will not reach full operating temp, so it dumps a lot more emissions than when it's up to

Two reasons this is bad: 1. Emissions, catalytic converters and such will not reach full operating temp, so it dumps a lot more emissions than when it's up to operating temp. Diesels were even worse in this regard cause the particulate filter plugs up when idling and then needs to trigger fuel wasting regen cycles. 2. Engine wear/damage. Oil pressures usually don't come up enough to properly lubricate components on the engine while cold idling for long periods of time. (Like, after the rpm's settle back down) This adds unnecessary wear. Should really only run an engine long enough to bring up initial oil pressure and then take it easy in it until it's up to full operating temp. (This is because parts expand at different rates, so pushing a cold engine hard will oftentimes blow seals)

swiley 7y ago
The second one isn’t a good reason to make something illegal. For some reason that doesn’t sound so crazy for Germany though. I’m not sure why.
- readarticle 7y ago
  It doesn’t sound out of the ordinary for any of the countries on the continent to my ears, different culture and all that.
- joecool1029 7y ago
  > The second one isn’t a good reason to make something illegal. I didn't say illegal, I said bad.
Unklejoe 7y ago
> Oil pressures usually don't come up enough to properly lubricate components on the engine while cold idling for long periods of time. I haven't seen this in practice. In fact, I see the opposite. My 2003 350z has an oil pressure gauge, and when it's idling while cold (say, < 40 degrees F), the pressure is actually higher than it is when cruising on the highway once it's warmed up. I attribute this to the oil being "thicker" when cold. On a really cold start, the pressure goes well beyond 60 PSI until the RPMs taper back down from around 1500 to the normal cold idle of ~1000, at which time it drops a bit.
- joecool1029 7y ago
  This is mostly correct observation with an incorrect conclusion. Oil pressures under load will be higher until oil temps come up. This is due to decreasing viscosity that improves the fuel flow. It still remains though that slower moving pump moves less oil (the volume doesn't change with temperature, just how quickly it falls back to the pan) and less oil even with a higher pressure may not provide adequate lubrication. The other major issue that specifically effects cold idling is that the ECM is going to increase the amount of fuel dumped into each cylinder, past what gets completely burned. This leads to problem called 'quench' that leaves gasoline behind on the walls of the cylinder after combustion. This will mix with the oil on these areas and actually dissolve it over time. Anyways, don't take it just from me. No manufacturer specifies over 30 seconds of idle time for their vehicles: https://info.ornl.gov/sites/publications/files/Pub61263.pdf https://info.ornl.gov/sites/publications/files/Pub61263.pdf
godshatter 7y ago
Not the parent poster, but I remote start my car so I don't have to sit inside it while it warms up enough to be able to drive. Is this not a thing anymore? I was always taught to warm the car up in cold weather so that the oil has had a chance to fully lubricate the engine so that you don't damage it if you have to accelerate quickly for whatever reason. Besides, I have to wait for the windows to defrost anyway. So why not let the car do that while I'm getting my coat on and shutting off the lights in the house and whatnot?
- jdsully 7y ago
  In older cars with worse tolerances and bad oil this was a major issue. Newer cars without carburetors ensure the proper fuel mixture even when cold. And multi viscosity oils ensure lubrication even when cold. Performance will still be worse and wear higher than a warm engine. But there’s no reason you can’t let it warm up on the way. Growing up in Canada it was always body rust not the engine that ultimately did the cars in anyways.
  - joecool1029 7y ago
    > Newer cars without carburetors ensure the proper fuel mixture even when cold. They also advance the timing when cold which increases emissions. I forgot to mention that as well. > And multi viscosity oils ensure lubrication even when cold. Improved, still not ideal.

swiley 7y ago

The second one isn’t a good reason to make something illegal. For some reason that doesn’t sound so crazy for Germany though. I’m not sure why.

readarticle 7y ago
It doesn’t sound out of the ordinary for any of the countries on the continent to my ears, different culture and all that.
joecool1029 7y ago
> The second one isn’t a good reason to make something illegal. I didn't say illegal, I said bad.

Unklejoe 7y ago

> Oil pressures usually don't come up enough to properly lubricate components on the engine while cold idling for long periods of time. I haven't seen this in practice. In fact, I see the opposite. My 2003 350z has an oil pressure gauge, and when it's idling while cold (say, < 40 degrees F), the pressure is actually higher than it is when cruising on the highway once it's warmed up. I attribute this to the oil being "thicker" when cold. On a really cold start, the pressure goes well beyond 60 PSI until the RPMs taper back down from around 1500 to the normal cold idle of ~1000, at which time it drops a bit.

joecool1029 7y ago
This is mostly correct observation with an incorrect conclusion. Oil pressures under load will be higher until oil temps come up. This is due to decreasing viscosity that improves the fuel flow. It still remains though that slower moving pump moves less oil (the volume doesn't change with temperature, just how quickly it falls back to the pan) and less oil even with a higher pressure may not provide adequate lubrication. The other major issue that specifically effects cold idling is that the ECM is going to increase the amount of fuel dumped into each cylinder, past what gets completely burned. This leads to problem called 'quench' that leaves gasoline behind on the walls of the cylinder after combustion. This will mix with the oil on these areas and actually dissolve it over time. Anyways, don't take it just from me. No manufacturer specifies over 30 seconds of idle time for their vehicles: https://info.ornl.gov/sites/publications/files/Pub61263.pdf https://info.ornl.gov/sites/publications/files/Pub61263.pdf

godshatter 7y ago

Not the parent poster, but I remote start my car so I don't have to sit inside it while it warms up enough to be able to drive. Is this not a thing anymore? I was always taught to warm the car up in cold weather so that the oil has had a chance to fully lubricate the engine so that you don't damage it if you have to accelerate quickly for whatever reason. Besides, I have to wait for the windows to defrost anyway. So why not let the car do that while I'm getting my coat on and shutting off the lights in the house and whatnot?

jdsully 7y ago
In older cars with worse tolerances and bad oil this was a major issue. Newer cars without carburetors ensure the proper fuel mixture even when cold. And multi viscosity oils ensure lubrication even when cold. Performance will still be worse and wear higher than a warm engine. But there’s no reason you can’t let it warm up on the way. Growing up in Canada it was always body rust not the engine that ultimately did the cars in anyways.
- joecool1029 7y ago
  > Newer cars without carburetors ensure the proper fuel mixture even when cold. They also advance the timing when cold which increases emissions. I forgot to mention that as well. > And multi viscosity oils ensure lubrication even when cold. Improved, still not ideal.