Do You Have To Keep The Engine Running For 10 Min On Cold Days?

[japthree]

My dad says that you should keep the engine running for a "good ten minutes" to warm up the car but is this for old cars? Any car 10 (?) years or younger this is superfluous and fuel is wasted?

[steve2006]

The days are gone when an engine needed "Running in" whether brand new or rebuild so is the warm up period especially so on modern aluminium block engines.

I think the proceedure is to start the engine and then drive straight away avoiding high revs until the engine is fully warmed.

Yes it is a waste of fuel to do so, an engine left idling takes longer to warm up than one being driven straight away so the cold start system will be active longer therefore wasting fuel.

[matt-c]

I'd still leave any car at least 30 seconds before driving away, if just to allow the oil to circulate fully

[LexIS200Sport]

I'd still leave any car at least 30 seconds before driving away, if just to allow the oil to circulate fully

same here :)

[wow300]

Drive it straight away, also tha t oil will be circulated very quick as long as oil pump is working proper.

[jpjsavage]

I have always been told to drive off straightaway.

[mikeyv]

Another drive off straight away vote from me.

Idling a cold engine will wash the bores with petrol, causing excessive wear - that was the theory a few years back anyway - whether the more sophisticated injection systems have changed that, I'm not sure, but I doubt it.

[LexIS200Sport]

Idling a cold engine will wash the bores with petrol, causing excessive wear

what exactly do you mean by "wash the bores with petrol"?

[mikeyv]

Idling a cold engine will wash the bores with petrol, causing excessive wear

what exactly do you mean by "wash the bores with petrol"?

The car will be running rich when cold, so there's a tendency for unburnt fuel to wash oil from the cylinder bores, thus causing wear.

As I said though, maybe modern (ish) fuelling systems are more efficient, causing less of a problem - even so, getting your engine up to temp as soon as possible has to be a good thing.

[matt-c]

You'll only get bore wash if the rings are knackered

[mikeyv]

The bore above the piston crown will be washed by excess petrol regardless of the state of the rings surely?

[matt-c]

Not enough to make any difference to the state of the engine. The piston rings are there to seal the bore (combustion chamber) and regulate the engine oil - basically so the oil and fuel don't mix. With a good condition cylinder, and good condition rings, there will be minimal fuel deposits on the bore wall, and what does make contact won't affect the bore, or rings, due to lubrication from the oil. You'll get no more bore wash from an idling engine than you will from an engine being driven.

[lexusdaduk]

but on cold frosty freezing mornings i leave it running, blow the fuel my arse needs warming.

[finest1]

i start engine and wait minimum 5-7 minutes before driving off. when i do drive off im not heavy on the acc pedal

[TigerFish]

Not enough to make any difference to the state of the engine. The piston rings are there to seal the bore (combustion chamber) and regulate the engine oil - basically so the oil and fuel don't mix. With a good condition cylinder, and good condition rings, there will be minimal fuel deposits on the bore wall, and what does make contact won't affect the bore, or rings, due to lubrication from the oil. You'll get no more bore wash from an idling engine than you will from an engine being driven.

Strange way to expalin things there mate. The oil ring isn't there to stop the oil and fuel mixing, it is there to stop too much oil being left in the bore and being burnt with the fuel and consuming large quantities of oil. Hence old, high mileage engines being smokey. The other ring(s) is/are there for compression purposes. The condition of the bore/rings wouldn't influence what fuel deposits where left on the bore. At the point of igniting the fuel, the piston will be travelling downwards, the rings cleaning off excess oil, and doing nothing to remove fuel from the bore. Only the burn would remove the fuel. If there is too much fuel, it would still be in the bores as the piston came back up to expel the gasses. Having said that, in modern engines I don't think that cars run rich enough to cause that kind of problem (the engine management is keeping track of things to the minute detail), rather than someone pulling a manual choke "on" to the max, or a temperature sensitive spring moving a choke automagically.

As far as my own start ups go, I don't really have any fixed rule. If i'm running late, I'll hit the road asap. If I'm clearing snow/ice, it'll be running warming the engine warming up, defrosting the rear screen and warming up the seats.

[Derek870]

Hit the Lecky heated seat button, luxury!

[brendangeorge]

but on cold frosty freezing mornings i leave it running, blow the fuel my arse needs warming.

I'm with you a warm chuff is worth a little fuel - I done it for 204K miles and my 430 runs like new. If your car is maintained correctly it will be fine and from a cold start will be ready to do what you want in 400m. It will be fine if warmed up as well.

Bren

[alphacat]

Thats very silly advice (leaving it running for 10 minites) The thing to do is to start and drive if possible.

In some EU countries it is illegal (belive it or not) to run the car idle without driving it on start up.

This is because when cold engines use much much more fuel and driving under load will warm them up quicker and reduce emmisions considerably on start up.

I am no fan of the Eu but I am a fan of people understanding the technology they use every day.

Its silly waiting you shoul drive off immediataely but keep the revs down and do not accelerate hard until the engine is at normal temperatures. waiting for 5 or 10 minutes is just wasteful.

Heat comes with work. Make it work it heats up quicker and reaches its operating temperature sooner. Result. Less wear less emmisions.

[Colin ck]

For any car with a turbo you used to have to idle the engine for about 40 seconds to allow the oil to circulate around the turbo bearings. Although I think modern oils allow toleration I still wait for about 30 seconds before I rev the engine.

When you come to a halt especially after a long fast run (eg Motorway fuel stop) wait about 10 seconds before switching the engine off, this allows the turbo to cool, preventing the oil cooking in the turbo, the hottest part of the engine. Again modern oils do their bit.

It's always better never to switch an engine off until the engine is thoroughly warmed up. This allows all water content to evaporate in the oil and the exhaust to dry out giving it a longer life. It is why the rear part of exhausts always rots first.

The original question about 'idling for 10 minutes' should have been interpreted as 'driven for 10 minutes' for reasons as above and also cars used to have dynamos with a maximum current output of 25 amps. It took 10 minutes or about 6 miles to put the charge back into the Battery.

[IHgs300]

I remember when my father used to put a paraffin heater under car during bad winters, Cant imagine anyone doing that now days. Just thing of the health and safety....LOL

[matt-c]

Colin - good points made about turbo's. It amazes me how "enthusiast" who own higher performance/tuned/modified or even just standard turbocharged cars (like Evo's, Skylines, etc) just get in, turn on, blast around straight away, then soon as they're on the drive shut it off. In the days I used to blat around in RS Turbo's and the like, I'd always keep it under 3k for the last min or so before reaching home, let it idle for 30 seconds or so before shutting it off. Those combined allow the turbine blades to slow down, so when you shut it off, they aren't still spinning at near peak rpm without any matching flowrate oil (or water if a water cooled turbo)

Regardless of the advice on modern cars, blah blah, I'll still always allow mine to sit and idle for minimum 30 seconds before driving off; as I said, it just allows the oil to fully circulate the engine before asking it to start doing anything. I can live with 30 seconds of idle fuel usage, and greenpeace can kiss my ***** :D

[alphacat]

For any car with a turbo you used to have to idle the engine for about 40 seconds to allow the oil to circulate around the turbo bearings. Although I think modern oils allow toleration I still wait for about 30 seconds before I rev the engine.

When you come to a halt especially after a long fast run (eg Motorway fuel stop) wait about 10 seconds before switching the engine off, this allows the turbo to cool, preventing the oil cooking in the turbo, the hottest part of the engine. Again modern oils do their bit.

It's always better never to switch an engine off until the engine is thoroughly warmed up. This allows all water content to evaporate in the oil and the exhaust to dry out giving it a longer life. It is why the rear part of exhausts always rots first.

The original question about 'idling for 10 minutes' should have been interpreted as 'driven for 10 minutes' for reasons as above and also cars used to have dynamos with a maximum current output of 25 amps. It took 10 minutes or about 6 miles to put the charge back into the battery.

I would agree with all of that.

Would add if anyone has had an RX8 (i dont recommend it) switching the engine off before its hot is often a disaster.!!