Cold morning engine warm-up

[cheffy]

Is is advised to let your engine, particularly a diesel, warm up before you set off, particularly in winter / cold mornings ! or is it best just to set off immediately ?

 

[C43AMG]

I always warm my turbo's up on the CL all year round

 

[whitenemesis]

Set off a soon as it is safe to do so i.e. windows clear.
Diesels do not warm easily at idle and really need to be worked (driven normally, don't use high revs) to warm up.

 

[saff]

I'm not sure what the official recommendation is, if there is one but I let mine idle for about half a minute before setting off. Even then I never push a cold engine and take it easy for a while until it begins to warm. I hate seeing cars cold starting then having the nuts revved off them. Just my idiosyncrasies I guess.

 

[190]

I set off pretty much the instant it starts but mines garaged. Obviously I don't use high revs straight away but I don't lug it either. The engine will warm up faster if you stay out of top gear and use moderate revs which will put some heat in the oil. Slogging along at 1000 RPM is a bad idea on a cold engine.

 

[clk320x]

I start the car up and set off around 15 seconds afterwards.

I use low revs/take it easy until the engine has reached operating temperature.

This is better than letting the engine idle for 15 mins to reach operating temp.

 

[Germgh0st]

I was always under the impression that the best way to warm any engine up is to drive it, not giving it any heavy right foot until it has warmed up.

 

[Bellow]

Oil flow is the issue.
Shockingly thick and resistant to flow when cold, too many rpm and the oil can't get to the bearings fast enough to protect them, too few rpm and and the pump's lack of delivery can leave a bearing starved.
The situation isn't helped by the oil taking about twice as long as the coolant to get to operating temp.
From gentle to mental progressively as the whole plot heats up.

 

[markjay]

I was always under the impression that the best way to warm any engine up is to drive it, not giving it any heavy right foot until it has warmed up.

As above.

The official advice is to drive off as soon as the oil pressure is stabilised. Sadly modern MB cars no longer have an oil pressure gauge, so the next best thing is wait a few seconds after starting the engine, then drive off, driving moderately until the engine reaches normal operating temperature.

The idea is that driving helps warm-up the engine quicker, so it spends less time running cold.

Minimising the amount of time the engine is running cold reduces wear, reduces fuel consumption, and reduces emissions.

(In addition, it's illegal to have the engine running while stationary, but that's to do with emissions regulations, not engine wear)

 

[cheffy]

Set off a soon as it is safe to do so i.e. windows clear.
Diesels do not warm easily at idle and really need to be worked (driven normally, don't use high revs) to warm up.

I thought this would be the case, I normally do that during the summer, I just wondered if winter was maybe a bit longer - thanks

 

[cheffy]

I'm not sure what the official recommendation is, if there is one but I let mine idle for about half a minute before setting off. Even then I never push a cold engine and take it easy for a while until it begins to warm. I hate seeing cars cold starting then having the nuts revved off them. Just my idiosyncrasies I guess.

I thought this may be the case, yes I also hate to see/hear peeps rev a cold engine, seen it at car auctions loads of times !

 

[cheffy]

As above.

The official advice is to drive off as soon as the oil pressure is stabilised. Sadly modern MB cars no longer have an oil pressure gauge, so the next best thing is wait a few seconds after starting the engine, then drive off, driving moderately until the engine reaches normal operating temperature.

The idea is that driving helps warm-up the engine quicker, so it spends less time running cold.

Minimising the amount of time the engine is running cold reduces wear, reduces fuel consumption, and reduces emissions.

(In addition, it's illegal to have the engine running while stationary, but that's to do with emissions regulations, not engine wear)

Thanks for that, I thought as much, re idling whilst stationery - well you have to clear / defrost / demist your screens etc !
Anyway, i am up a private secluded driveway, and set of at 6am each morning, so doubt if I'd get caught anyway LoL

 

[Bellow]

While it is true that leaving it idling will take ages to get fully to temp, while it is, it is warming and with the internal loads/forces as low as they can be. That initial phase can be commenced as soon as the car is opened. Seatbelts, screen clearing and all other pre-drive faffing can be done while the engine is commencing its warm up and when least loaded. Fire first, faff second.

 

[Deleted member 126251]

The other point is that if you warm the engine before driving off, the rest of the car is still frozen - transmission, steering box, wheel bearings, suspension etc.

It always bemuses me to see folk speeding off down the road after leaving it idling for 15 minutes to "warm up'.

 

[Bellow]

The other point is that if you warm the engine before driving off, the rest of the car is still frozen - transmission, steering box, wheel bearings, suspension etc.

It always bemuses me to see folk speeding off down the road after leaving it idling for 15 minutes to "warm up'.

With the exception of an auto box and PAS none of those have pumped oil systems and those two have them primarily as hydraulic not protective systems. None see combustion heat. Engine heat will conduct into a gear box and the churning in a TC will heat the entire auto box - as an engine idles.
Greased bearing (eg wheel) don't care about temperature (providing it is within the grease's wide temp range) suspension bushes aren't going to be overly troubled. Back to the engine then.

 

[Deleted member 126251]

With the exception of an auto box and PAS none of those have pumped oil systems and those two have them primarily as hydraulic not protective systems. None see combustion heat. Engine heat will conduct into a gear box and the churning in a TC will heat the entire auto box - as an engine idles.
Greased bearing (eg wheel) don't care about temperature (providing it is within the grease's wide temp range) suspension bushes aren't going to be overly troubled. Back to the engine then.
.

I'm pretty sure there is oil in the gearbox of my car.

I have an oil temperature gauge in my car. In temperatures of just above freezing (bearing in mind that my car is garaged (which is partly insulated and the car is warmer than standing outside) ) it takes at least 10 minutes of calm driving to get the water temp upto normal operating temp. It then takes several more miles of driving after that, before the oil temp needle goes into the recommended operating temperature.

I'll stick to starting and driving off as soon as it is safe to do so instead of "warming up the engine at idle".

 

[Bellow]

I'm pretty sure there is PUMPED oil in the gearbox of my car.
.

FTFY.

 

[190]

This business about oil taking time to flow.

First of all it's why we use the multigrade oils that we do. If anyone is concerned about this and the car lives outside then you have a choice to use an oil that's thinner when cold. For example 0W30 instead of 5W30. To be honest even the 5W30 will be good enough in our typical climate.

Secondly the issue of cold flow doesn't really affect the crank bearings as your oil pump is a positive displacement device. Within reason the oil has no choice but to flow at the rate at which it's pumped, although the oil pump and pressure loss will consume more power from the engine with thicker oil. Cold oil flow may delay delivery of oil to the top end which would be a legitimate concern but this can be allowed for in a driving off delay of 2 seconds.

I will never be persuaded that warming up at idle is anything but bad for the engine and exhaust system. I set off near instantly, just a couple of secs delay to allow the top end to quieten down indicating oil has reached it and the cam chain tensioner has been pressurised.

 

[Bellow]

This business about oil taking time to flow.

First of all it's why we use the multigrade oils that we do. If anyone is concerned about this and the car lives outside then you have a choice to use an oil that's thinner when cold. For example 0W30 instead of 5W30. To be honest even the 5W30 will be good enough in our typical climate.

Get some hands on experience of the change if viscosity of fluids with temperature. Get some e-liquid and 5ml syringe and needle and see how it is nearly un-pumpible at room temp and like water when made hot. The difference in effort required in each case is eye opening.

Secondly the issue of cold flow doesn't really affect the crank bearings as your oil pump is a positive displacement device. Within reason the oil has no choice but to flow at the rate at which it's pumped, although the oil pump and pressure loss will consume more power from the engine with thicker oil. Cold oil flow may delay delivery of oil to the top end which would be a legitimate concern but this can be allowed for in a driving off delay of 2 seconds.

Choked flow. All I need to say.

I will never be persuaded that warming up at idle is anything but bad for the engine and exhaust system. I set off near instantly, just a couple of secs delay to allow the top end to quieten down indicating oil has reached it and the cam chain tensioner has been pressurised.

That's your view, fine. But the exhaust does not suffer and neither does an engine by letting it warm.
Driving off 'near instantly' compared to warm up at idle. Both have the exact same oil flow circumstance, one has vastly increased forces ( the forces that the oil film has to cope with) due to load and increased (non-linear) inertial forces. Not to mention tolerances wider than desirable, and the excess fuel required to drive (still very rich) which will wash the bores of oil and the case for just driving off is far from made.

 

[190]

Thanks but I already have hands on experience of how viscosity changes with temperature and how a positive displacement pump gives oil little choice but to flow up to the point of the relief valve setting. I'm still generally a fan of thinner oil for the reduced drag at low temperatures purely because it reduces losses, not because I have concerns about the engine being lubricated without an idle warm up.

Mercedes recommend oil grades for given temperature ranges and it works. They don't recommend warm up of any duration before driving off.