Cold start question

Raymond Lin · 20 Jan 2018 at 12:35

I remember watching a video on Jay Leno’s channel and he mentioned that when starting one of his Ferrari (or one of the Italian exotics) that he waits for the engine oil needle lifts just that little bit before setting off, and it helps to keep the engine healthy because where the cars are made, a warmer climate so in a colder climate, he does it to protect the engine.

Is there any truth to this? Do people do this or at least wait until the Rev counter drops to idle after the initial spike on cold start.

Howard · 20 Jan 2018 at 12:41

Start the engine, wait a brief moment (10-30 seconds) for the oil to begin circulating, drive off. Keep revs and engine load fairly low for the first few miles or so. An exotic, hand-built engine might need more TLC but doing anything different in a modern mass-produced car is not necessary and not good practice.

sigma · 20 Jan 2018 at 12:41

I've heard people state it's best to have some oil pressure built up before driving off, not long, probably 10 seconds or so.

I've noticed a lot of people pull off as soon as the engine is on, literally within milliseconds of turning the key they're off.

tom_nieto · 20 Jan 2018 at 12:58

Better to set off fairly promptly and keep the engine below 3,000 rpm until the oil is fully up to temperature. Not sure about ageing exotics though!

Zico · 20 Jan 2018 at 14:08

From a cold start the dynamic mpg reading on my FiST will start at 0.5mpg for around 20-30 seconds before there is a notable change in engine sound and the mpg reading changes to 0.2mpg. I set off after this change.

LiE · 20 Jan 2018 at 15:31

Also heard it's good to let a turbo cool down if you've had a spirited drive some where, rather than switch the ignition off immediately.

Raymond Lin · 20 Jan 2018 at 15:37

LiE said:
Also heard it's good to let a turbo cool down if you've had a spirited drive some where, rather than switch the ignition off immediately.

I heard that too, meant to sit there idle for a minute. I have never done that because the last few miles home is limited to 30mph always with traffic so even if i gave it some beans earlier, the last 10mins it's poodle slow, easy on the pedal driving.

Lashout_UK · 20 Jan 2018 at 15:46

Yea, I always let my engines idle for a little while – usually while I'm just setting up nav/music/mirrors/whatever. I've only a short drive until I'm on the motorway, so I prefer them to a have a little heat in them before I hit that.

Many classics are far more sensitive to temperature; letting them warm a little not only reduces the chance of any problems, it also makes them far easier to drive. Similarly, ideal to just let them idle for a few moments before shutting down, too (same as you would an older turbocharged car).

agw_01 · 20 Jan 2018 at 15:46

Oil pressure is generally fully built as soon as the engine has started but nothing wrong with giving the car 10-20 seconds to idle for things to settle down before driving off.

Echo what's been said really, keep the revs and engine load low until the oil has warmed up. Oil takes a lot longer to warm up than coolant so don't go off the car's temperature gauge unless it specifically mentions being an oil temperature gauge. 15-20 mins of normal driving should suffice.

The whole turbo cooling down thing is because turning off when the turbo is very hot can cause oil to solidify and therefore reduce the size of the oilway inside the turbo. Not so much of a problem with water cooled turbos but definitely no harm in driving gently for the last leg home. Leaving it to idle is fine but you'll get no airflow to aid in cooling things down.

I guess a very highly tuned carburettor motor may need a bit of heat into it before it'll idle/run properly but this shouldn't be a problem on a modern fuel injected car.

mrk · 20 Jan 2018 at 15:50

sigma said:
I've heard people state it's best to have some oil pressure built up before driving off, not long, probably 10 seconds or so.

I've noticed a lot of people pull off as soon as the engine is on, literally within milliseconds of turning the key they're off.

Doesn't really matter on modern cars though. Having the car sit idle for too long also means all components aren't warming up at the same time, diff, gearbox, engine, brakes etc. As long as the fuel line is primed (the noise you hear when you turn the key to position 2), then once the car is started after a few seconds, you can just drive off. If there is a specific process for your car, it will be noted in the manual for starting in cold conditions.

Some cars have variable redlines that go higher as the engine, oil and water temp reaches optimal levels. On a really cold morning mine starts with a 4000rpm redline which takes around 5 miles of driving to reach normal operation in 500rpm increments. Basically when the oil reaches around 85 degrees. The funny thing is that by the time I drive to the end of my road, the heater vents are blowing warm air. Cabin warms up insanely quickly :cool:

Edit*

Also worth noting that your car (along with all other modern cars) will have a warmup feature on cold starts that is specifically designed for this very reason. Everything has been engineered to keep the engine in check on cold starts. You'll notice the warmup phase lasts 30-60 seconds /if/ you leave it idling, then the whole exhaust and engine tone changes to something more neutral and settled down.

Lashout_UK · 20 Jan 2018 at 16:26

mrk said:
Edit*

Also worth noting that your car (along with all other modern cars) will have a warmup feature on cold starts that is specifically designed for this very reason. Everything has been engineered to keep the engine in check on cold starts.

That's for emissions purposes (higher idle, etc – gets the catalytic converters lit up); it's nothing to do with getting the engine up to temperature, although it does have that beneficial effect to a degree.

Even a modern engine benefits from being allowed to idle for a brief period. I'm not talking minutes, here, but not just turning the key and driving off. Oil starts flowing, gets where it needs to be, fuel starts vapourising properly, metals and plastics get a little less brittle, clearances start to settle; everything starts running just as it should.

Unlikely to make a difference in your ownership of the car, but I always just treat it as a little preventative maintenance. Particularly with something a little more highly strung, or older.

Raymond Lin · 20 Jan 2018 at 16:37

Lashout_UK said:
That's for emissions purposes (higher idle, etc – gets the catalytic converters lit up); it's nothing to do with getting the engine up to temperature, although it does have that beneficial effect to a degree.

Even a modern engine benefits from being allowed to idle for a brief period. I'm not talking minutes, here, but not just turning the key and driving off. Oil starts flowing, gets where it needs to be, fuel starts vapourising properly, metals and plastics get a little less brittle, clearances start to settle; everything starts running just as it should.

Unlikely to make a difference in your ownership of the car, but I always just treat it as a little preventative maintenance. Particularly with something a little more highly strung, or older.

I wait until the needle for the rev counter to drop and the exhaust note changes, it takes about 20s.

sigma · 20 Jan 2018 at 17:47

mrk said:
Doesn't really matter on modern cars though. Having the car sit idle for too long also means all components aren't warming up at the same time, diff, gearbox, engine, brakes etc.

Do you class ~10 seconds as too long?

sigma · 20 Jan 2018 at 17:50

agw_01 said:
Oil pressure is generally fully built as soon as the engine has started but nothing wrong with giving the car 10-20 seconds to idle for things to settle down before driving off.

Echo what's been said really, keep the revs and engine load low until the oil has warmed up. Oil takes a lot longer to warm up than coolant so don't go off the car's temperature gauge unless it specifically mentions being an oil temperature gauge. 15-20 mins of normal driving should suffice.

The whole turbo cooling down thing is because turning off when the turbo is very hot can cause oil to solidify and therefore reduce the size of the oilway inside the turbo. Not so much of a problem with water cooled turbos but definitely no harm in driving gently for the last leg home. Leaving it to idle is fine but you'll get no airflow to aid in cooling things down.

I guess a very highly tuned carburettor motor may need a bit of heat into it before it'll idle/run properly but this shouldn't be a problem on a modern fuel injected car.

My neighbours car is moving within milliseconds and then he floors it down the road.

Similar thing takes place in work car park, then as soon as they hit the road that 4 pot diesel is flat out as they race to sit in the nearest bit of traffic.

Kenai · 20 Jan 2018 at 17:56

sigma said:
My neighbours car is moving within milliseconds and then he floors it down the road.

Similar thing takes place in work car park, then as soon as they hit the road that 4 pot diesel is flat out as they race to sit in the nearest bit of traffic.

That's just because ragging the absolute balls off it is the only way to get your average 2.0 TDI to move anywhere faster than walking

mrk · 20 Jan 2018 at 18:05

sigma said:
Do you class ~10 seconds as too long?

No, 10 seconds is about the norm, get in prime, start, click-clunk the belt, set the radio to Spotify, begin moving off :cool:

CaptainRAVE · 20 Jan 2018 at 18:11

Jump in, drive off. Generally monitor oil temp. Actually surprises me every time how long it takes to warm up. Saying that, I have put my foot down with a cold engine a few times. It isn’t like I keep them for long anyway.

JBuk · 20 Jan 2018 at 18:30

I go as soon as the engine is started, if I was driving something expensive or exotic I’d probably let the engine warm up

Finglonga · 20 Jan 2018 at 19:08

LiE said:
Also heard it's good to let a turbo cool down if you've had a spirited drive some where, rather than switch the ignition off immediately.

Not needed on modern cars as they all have pumps to circulate oil after the engine is shut off.

agw_01 · 20 Jan 2018 at 23:16

sigma said:
My neighbours car is moving within milliseconds and then he floors it down the road.

Similar thing takes place in work car park, then as soon as they hit the road that 4 pot diesel is flat out as they race to sit in the nearest bit of traffic.

It's just ignorance. People don't know or care about these things. Even if you try to explain, it's just too much hassle for them to comprehend showing a bit of mechanical sympathy. Even some owners of performance cars don't even understand the reasoning behind it. How can you be a car enthusiast yet not know about basic engine care?

@Finglonga, good shout. Many cars have auxiliary electric water pumps for this very reason. Even on old cars, the heat transfer within the cooling system once the engine is shut off will cause the coolant to continue to flow. You will sometimes hear the car 'gurgling' as a sign that this is happening.