Should You Warm Up Your Car Before Driving?

[Wolf359]

Originally Posted By: supton
Higher rpm, heats up faster. More importantly, it probably heats up the catalyst faster. There are cold start limits to be obeyed. Also, I wonder if the higher rpm helps with transmissions: a manual trans will heat up a bit, even in neutral. I could tell in my TDI what a few minutes of idling would for shifting. An automatic is no different, although the pump likely makes far more heat (then again, thin ATF shouldn't need much heating I'd think).


Yeah, that was normal for the Taurus that I had before. Other thing would be that the transmission needed to heat up too before the lock up torque converter would kick in. It just wouldn't engage til the fluid was warmer, seemed to take about 5 miles or so in the cold, only a mile or two in regular weather. It was easy to tell as the rps would be about 200 higher if the lockup didn't kick in.

 

[69GTX]

Originally Posted By: blupupher
From they way I understand it, a 5w-30 oil starts out "thin" when it is cold and as it warms up and approaches operating temp, it thickens to a 30 wt oil. Once you go above 100°C it will start to thin out again.

Or have I misunderstood this all the time. I know 5w is the winter rating, but above is how I understood it works.



Oil is the thickest before you cold start the car. The colder it is outside, and the longer the car has sat, the lower the viscosity...regardless if it's a multi-grade or straight weight oil.

From that point on, the oil only gets thinner as oil temp rises. It would be ideal if the oil at startup were around 8-14 cSt (operating viscosity ranges). It's actually up to 1,000X to 3,000X that during an extreme cold start in say -35/-40 deg C temps. Time to read the new Motor Oil University...or even the old one.

 

[HonorAndHonesty]

I live on a State Highway so once I leave my driveway its 0 to 55 up a slight hill when I leave for work, so I try to warm up the car for a minute or two if its summer and in the winter I let it heat up for 10 to 20 minutes, longer if its outside and we get an ice storm or something.

I always figured it was easier on the head gaskets and catalytic converter(s)ect... if it warmed up gradually, however this is not the main reason I warm the car up.

I have left the driveway on a stone cold engine at zero degrees and floored it from 0 to about 70, but it was in a work truck and it was an urgent call. No immediate ill affects. I got heat a bit quicker that way.

 

[HonorAndHonesty]

FWIW, When I had our 2013 Prius which was a lease vehicle I would sometimes leave the driveway in cold weather without a warmup, pulling right onto a 55mph road, and I noticed that the engine would idle along and most of the propulsion was done with the electric motor until I hit about 30mph or so. It was definitely a different curve from when the car was heated up.

I believe this was likely done for emissions purposes rather than engine longevity purposes. I figure they tried to reduce engine revs until the cat lit off, which was extremely quick, driving or Idling. Watching the cat temps on my scanner confirmed this, this car got that cat lit off quick.

Now I also have a 05 sienna and a 09 XB, and the sienna delays shifting into higher gears until the engine warms up a bit, it holds the revs in each gear even at light throttle input, I believe this is in an attempt to get the Cat heated up as quickly as possible to minimize emissions. I do not believe that I can see cat temps on the sienna with my torque app so I really cant confirm if the modified shifting algorithm is a function of coolant temp or cat temp.

The 09 XB has a similar behavior when cold, Its kind of frustrating but what can you do. They want that cat to light off as quick as it possibly can.

 

[blupupher]

Originally Posted By: 69GTX

Oil is the thickest before you cold start the car. The colder it is outside, and the longer the car has sat, the lower the viscosity...regardless if it's a multi-grade or straight weight oil.

From that point on, the oil only gets thinner as oil temp rises. It would be ideal if the oil at startup were around 8-14 cSt (operating viscosity ranges). It's actually up to 1,000X to 3,000X that during an extreme cold start in say -35/-40 deg C temps. Time to read the new Motor Oil University...or even the old one.


Well, I started searching and see where I was confused.
A 5w-30 oil is thinner @ 40°C than a straight 30 wt oil @ 40°C (which is where i was thinking as it warms up it turns into a 30 wt), but a 5 wt oil is thicker @ 40°C than a 30 wt oil @ 100°C.

So I was wrong about that, now I better understand it. Disregard my previous comment.

 

[CrAlt]

Ya normally 15-25mins in the winter.

 

[bunnspecial]

I do like other folks on FI vehicles-I wait until the idle starts to drop and then go easy on them. On my usual commute, the needle is starting to move by the time I hit the interstate, so I just keep a light foot while I'm on the on-ramp.

When I do something crazy like drive a carbureted car in 15º weather, I do have to give it some warm up. My usual rule of thumb(regardless of outside temperature is to let it warm up until it's stable with 1/3 choke or less. In warmer temperatures that usually happens within a few seconds of starting, while it can take a couple of minutes in cold weather. Otherwise, I consider it dangerous to drive as there's absolute no low end torque and in cold temperatures it will die with too much throttle even when choked.

 

[edyvw]

Originally Posted By: supton
Originally Posted By: edyvw
My HVAC is ALWAYS on cold! I set it up on cold before I turn off car night before. What that does is that it cuts off secondary radiator, so outside air will not prevent coolant reaching temperature fast because there is a flow of air thru secondary radiator. Keep vent on off or min just to keep windows clear.


I believe you are wrong on this one--mixing valves went away a long time ago. These days the heater core gets full coolant flow always; and instead the mixing valve is actually a flap that allows/disallows airflow over the heater core. I don't know when the changeover was (and of course not everyone did it on the same day).

But I agree with you: turn the fan off, and the car should warm up faster. No airflow over that "radiator". But do try to argue that with SWMBO and see if your logic prevails.

Well my X5 has very sophisticated HVAC system, and I fallow actual temperature in celsius. As soon as you turn on heat there is rush of cold water since there is 10-15 degrees drop immediately!
Maybe it is on some cars, but i would say it is more exception then rule.

 

[edyvw]

Originally Posted By: KrisZ
Originally Posted By: edyvw
AGAIN? I thought in this digital age this ridiculous myth would die.
OP, you are running PP 5W30 in very, extremely, uber whatever simple engine.
What I do is that I turn on car, by the time I put seat belt on, turn on seat warmers, music, it is like 10 seconds. Then I back up from garage without touching pedal, that is another 30-45 doing it slowly.
My HVAC is ALWAYS on cold! I set it up on cold before I turn off car night before. What that does is that it cuts off secondary radiator, so outside air will not prevent coolant reaching temperature fast because there is a flow of air thru secondary radiator. Keep vent on off or min just to keep windows clear.
Stay up to 2500 rpms. After 5 min slowly start using heat. This method will warm up your car much faster then any idling in drive way.


It feels great to dispel one myth while being a slave to another, doesn't it?

Really, so your answer is being slave to another. Do enlighten me!
I can actually follow temperature on phone and when you turn heat there is sudden drop of temperature as water from heater core is released.
I posted very detail explanation, so go ahead...

 

[itguy08]

Originally Posted By: edyvw

Well my X5 has very sophisticated HVAC system, and I fallow actual temperature in celsius. As soon as you turn on heat there is rush of cold water since there is 10-15 degrees drop immediately!
Maybe it is on some cars, but i would say it is more exception then rule.


If your X5 is the Diesel in your sig, that explains it. Diesels take a long time to warm up (many in the pickups have supplementary electric heaters) so a mixing valve may still be needed to help the engine warm quicker.

In my "low tech" Fords (and the Infiniti prior) I'd set the temp at 71 or 72 and there would be a delay for the fan to kick in until there was some heat coming out of the vents. There was no mixing valve on either - the hoses run right into the heater core.

I'd say your BMW is the exception rather than the rule.

 

[Wolf359]

Originally Posted By: edyvw

Well my X5 has very sophisticated HVAC system, and I fallow actual temperature in celsius. As soon as you turn on heat there is rush of cold water since there is 10-15 degrees drop immediately!
Maybe it is on some cars, but i would say it is more exception then rule.


You turn on the heat? I've had climate control for 10+ years, I never turn it on, it's always set between 70-76. It comes on automatically once the car heats up a little. You get nothing when you first turn the car on although I take an extra second or two to turn on the seat heaters.

 

[edyvw]

Originally Posted By: Wolf359
Originally Posted By: edyvw

Well my X5 has very sophisticated HVAC system, and I fallow actual temperature in celsius. As soon as you turn on heat there is rush of cold water since there is 10-15 degrees drop immediately!
Maybe it is on some cars, but i would say it is more exception then rule.


You turn on the heat? I've had climate control for 10+ years, I never turn it on, it's always set between 70-76. It comes on automatically once the car heats up a little. You get nothing when you first turn the car on although I take an extra second or two to turn on the seat heaters.

I shut down all systems and put HVAC to cold before turning off the car.
BMW's for the U.S. market are set up to start vent immediately even if you turn it off night before. However, I coded that option to not start unless I press vent. button. As I stated earlier, car do need more time if heat is on (set up lets say 70-76) to warm up then if I start and drive 4-5 minutes with HVAC on cold.
However, I generally hate car doing stuff for me, so unless it is summer and I have my baby in car, or need to defog windows in winter, I do not even touch AC or Auto AC. Even auto AC is just in rare circumstances.

 

[edyvw]

Originally Posted By: itguy08
Originally Posted By: edyvw

Well my X5 has very sophisticated HVAC system, and I fallow actual temperature in celsius. As soon as you turn on heat there is rush of cold water since there is 10-15 degrees drop immediately!
Maybe it is on some cars, but i would say it is more exception then rule.


If your X5 is the Diesel in your sig, that explains it. Diesels take a long time to warm up (many in the pickups have supplementary electric heaters) so a mixing valve may still be needed to help the engine warm quicker.

In my "low tech" Fords (and the Infiniti prior) I'd set the temp at 71 or 72 and there would be a delay for the fan to kick in until there was some heat coming out of the vents. There was no mixing valve on either - the hoses run right into the heater core.

I'd say your BMW is the exception rather than the rule.

Yeah, diesels do need more time for coolant and especially oil (8qt sump).
However, 35i works same way. I think European cars are generally set up this way then. Tiguan works same way, as well as all my previous cars.

 

[OVERKILL]

Originally Posted By: edyvw
Originally Posted By: itguy08
Originally Posted By: edyvw

Well my X5 has very sophisticated HVAC system, and I fallow actual temperature in celsius. As soon as you turn on heat there is rush of cold water since there is 10-15 degrees drop immediately!
Maybe it is on some cars, but i would say it is more exception then rule.


If your X5 is the Diesel in your sig, that explains it. Diesels take a long time to warm up (many in the pickups have supplementary electric heaters) so a mixing valve may still be needed to help the engine warm quicker.

In my "low tech" Fords (and the Infiniti prior) I'd set the temp at 71 or 72 and there would be a delay for the fan to kick in until there was some heat coming out of the vents. There was no mixing valve on either - the hoses run right into the heater core.

I'd say your BMW is the exception rather than the rule.

Yeah, diesels do need more time for coolant and especially oil (8qt sump).
However, 35i works same way. I think European cars are generally set up this way then. Tiguan works same way, as well as all my previous cars.


Can you clarify how you are saying they are setup? Because both my E39 M5 and my sister's E46 330i had/have "auto" climate control and we just left/leave them at 21.5C and the cars won't run the fan until there's a bit of heat into the coolant, and then it slowly ramps up the fan speed, so you aren't blasted with cold air.

 

[edyvw]

Originally Posted By: OVERKILL
Originally Posted By: edyvw
Originally Posted By: itguy08
Originally Posted By: edyvw

Well my X5 has very sophisticated HVAC system, and I fallow actual temperature in celsius. As soon as you turn on heat there is rush of cold water since there is 10-15 degrees drop immediately!
Maybe it is on some cars, but i would say it is more exception then rule.


If your X5 is the Diesel in your sig, that explains it. Diesels take a long time to warm up (many in the pickups have supplementary electric heaters) so a mixing valve may still be needed to help the engine warm quicker.

In my "low tech" Fords (and the Infiniti prior) I'd set the temp at 71 or 72 and there would be a delay for the fan to kick in until there was some heat coming out of the vents. There was no mixing valve on either - the hoses run right into the heater core.

I'd say your BMW is the exception rather than the rule.

Yeah, diesels do need more time for coolant and especially oil (8qt sump).
However, 35i works same way. I think European cars are generally set up this way then. Tiguan works same way, as well as all my previous cars.


Can you clarify how you are saying they are setup? Because both my E39 M5 and my sister's E46 330i had/have "auto" climate control and we just left/leave them at 21.5C and the cars won't run the fan until there's a bit of heat into the coolant, and then it slowly ramps up the fan speed, so you aren't blasted with cold air.


Mean, set up with mixing valves, where you can prevent circulation by keeping it on cold, which would be 16 degrees.
Yes, keeping it on auto will not blast air but it will allow coolant to circulate thru heater core, which will increase time to warm up (we are talking minutes here, especially on M5). For example, fallowing coolant parameters on Carly, I can notice that once I turn on heat (regardless of fan speed) there is 10-15c drop in coolant temperature, meaning there is sudden rush of cool coolant to the system. If I let's say start car and turn it on 22c, car needs almost 8-10min longer to reach same temperature if outside air is around 2c. That would be of course shorter in gas engine.
I am not sure on E39 (I had E34 before) whether yours would start fan even if your auto is off? I just recoded that not to turn on automatically

 

[OVERKILL]

IIRC, when it was off, it stayed off, even on a clean start.

And yes, the M5 took a while to make heat. I blame the massive mechanical fan and huge rad, LOL!

 

[edyvw]

Originally Posted By: OVERKILL
IIRC, when it was off, it stayed off, even on a clean start.

And yes, the M5 took a while to make heat. I blame the massive mechanical fan and huge rad, LOL!

Yeah, so E39 had good old HVAC that you were in charge of. E60/70 would start vent in the morning regardless whether you turned it off night before or not. Probably set up so people can "save time."
Good thing it is possible to code it which means it is different for different markets.

 

[Shannow]

Originally Posted By: 69GTX
Oil is the thickest before you cold start the car. The colder it is outside, and the longer the car has sat, the lower the viscosity...regardless if it's a multi-grade or straight weight oil.

From that point on, the oil only gets thinner as oil temp rises. It would be ideal if the oil at startup were around 8-14 cSt (operating viscosity ranges). It's actually up to 1,000X to 3,000X that during an extreme cold start in say -35/-40 deg C temps. Time to read the new Motor Oil University...or even the old one.


I disagree...if the oil was at operational viscosity at startup, it would need all the AW additives to be fully functional from dead cold...which they don't.

The thicker, cold oil does a fair bit of hydrodynamic lubrication in the period between first start, and thin/additive controlled wear.

 

[KrisZ]

Originally Posted By: edyvw
Really, so your answer is being slave to another. Do enlighten me!
I can actually follow temperature on phone and when you turn heat there is sudden drop of temperature as water from heater core is released.
I posted very detail explanation, so go ahead...


I read you post carefully. You claim that one practice is a myth, i.e idling the car to prolong its life, while you developed your own ritual because it shaves off few minutes in reaching operating temp. Why do you think you should do it?
If the answer is to prolong engine life, then you substituted one myth for another.

 

[WhizkidTN]

I pretty much follow the advice given in the video, even in warmer weather because I want my engine fully up to operating temperature before I put much of a heavy load on it (like aggressive freeway merging for example).