caledoniandream:
I am in here with Newmercman, give it time to warm up.
The reason that manufacturers don’t want you to idle has more to do with fuel economy than being thoughtful with their engines.
There is so much pressure on low emissions and low fuel usage.
It’s ok to say “don’t use full throttle" when cold, but how are you going to this in today’s traffic?
Mostly you have to be full on in today’s rat race.
30 years ago I worked for a haulier in a little village, in the morning we warmed the engine up, than drove no faster than 10 mile p/h to the next village.
On certain mornings, his old man would be in the next village checking if we not went to fast to early.
If I would do that now, people would phone the police complaining that I was holding up the traffic.
I was told by a friends husband who works as a mechanic for the Paris Dakar rallies that you should let the engine sit for 5 minutes or so then move off and keep the revs low.
newmercman:
If you’ve ever tried to pour oil from a can at low temperatures, you’ll know exactly why you should let it warm up before you force it around an engine.
And how on earth does a driver warm the oil without forcing it around the engine?
There simply is no support for the idea that engines should be left to idle. Cold oil is no worse at lubrication than hot oil - it is simply that the viscosity changes with temperature, which is why modern oils have additives which maintain their viscosity across a temperature range. Cold engines also have looser tolerances, which is why the oil should be relatively thicker at cold than it would be with everything at operating temperature.
Perhaps things were different in the days of engines running on whale oil or whatever, when in cold temperatures the oil might have been closer to grease and far too thick for the tolerances of a cold engine (i.e. the temperature variability in viscosity did not match the temperature variability in tolerances), but that will be before the careers, if not the lifetimes, of drivers today. I think multi-viscosity oils have been around since the 50s.
And as others have pointed out, the only sensible reason for avoiding wear on an engine would be to avoid the cost of repairing or replacing it, but idling itself costs money, and mechanical wear of engine parts is nowadays something that is rarely a problem within the lifetime of the vehicle itself (and is usually caused in consequence of some other problem, not just ordinary use).
The days when engines had to be overhauled at great expense every few thousand miles, making it worthwhile to waste a bit of fuel to eek out more time between rebuilds, are also long gone.
Perhaps the persistence of this myth is because, having spent donkeys’ years wasting fuel unecessarily, perhaps even paying out of their own pockets if they are an owner driver, those responsible have to believe that they were (and are) doing it for a good reason.
Old habits die hard. I think it’s just because people think it feels right.
Relating to other IC engines. On large supercharged piston engined twins we limited the excessive idling time at cold for similar reasons. The bores wore at cold idle due to un burnt fuel depositing on the liners acting as a solvent to the oil. The scavenge rings would pull the small fuel deposits into the lubrication system. Granted this is a petrol thing but idle combustion also created ignition problems due carbon depositing.
However. Manufacturers are always tweaking start up aid systems so just follow the procedures in the manual. Unless you’re one of the conspiracy theorists .
Radar19:
I was told by a friends husband who works as a mechanic for the Paris Dakar rallies that you should let the engine sit for 5 minutes or so then move off and keep the revs low.
Race spec engines are very different beasts to road engines, many will need pre-heaters, before even starting and they aren’t expected to run for a million miles.
I’ve worked on teams where the pre-heaters have been on timers and start running before we arrive at the circuit and many hours before the car goes out on track. Where they are started run upto temperature, switched off, to let the heat soak into the gearbox, then run again to to go through the gears.
newmercman:
If you’ve ever tried to pour oil from a can at low temperatures, you’ll know exactly why you should let it warm up before you force it around an engine.
It’s still going to be “forced around the engine” while you sit at idle for 10 minutes “letting it warm up”. The moving parts will still be rubbing against one another for all that time, possibly receiving sub-optimal lubrication due to the viscosity of the oil and low revs. Get the thing on the road under a light load and it’ll warm up much more quickly, resulting in less time spent with thick oil being “forced around the engine”.
newmercman:
If you’ve ever tried to pour oil from a can at low temperatures, you’ll know exactly why you should let it warm up before you force it around an engine.
It’s still going to be “forced around the engine” while you sit at idle for 10 minutes “letting it warm up”. The moving parts will still be rubbing against one another for all that time, possibly receiving sub-optimal lubrication due to the viscosity of the oil and low revs. Get the thing on the road under a light load and it’ll warm up much more quickly, resulting in less time spent with thick oil being “forced around the engine”.
Except that the forces are much lower at idle than they are at higher engine speeds, seeing as how the oil pump is gear driven and therefore pumps more oil as rpms increase.
That’s my answer to the question asked, if anybody wants to start up and go, that’s up to them, I’m just saying what I do with my engines. I’m convinced I’m doing it right and my oil analysis confirms that, I have very little wear metals in my samples (i drop the oil at 15,000miles in the CAT and 25,000 in the Volvo) and oxidation and nitration, which are indicators of excessive idling are at zero.
I don’t do it the other way to compare, so I can’t say one way is better than the other for certain, but my way works for me and as it all comes out of my pocket, it’s my choice to make.
newmercman:
Except that the forces are much lower at idle than they are at higher engine speeds, seeing as how the oil pump is gear driven and therefore pumps more oil as rpms increase.
That’s my answer to the question asked, if anybody wants to start up and go, that’s up to them, I’m just saying what I do with my engines. I’m convinced I’m doing it right and my oil analysis confirms that, I have very little wear metals in my samples (i drop the oil at 15,000miles in the CAT and 25,000 in the Volvo) and oxidation and nitration, which are indicators of excessive idling are at zero.
I don’t do it the other way to compare, so I can’t say one way is better than the other for certain, but my way works for me and as it all comes out of my pocket, it’s my choice to make.
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It doesn’t matter whether the forces (at the oil pump) are lower or higher - letting the engine warm up slowly means that it spends more time with cold, thick oil being pushed (slowly) through the bearings etc. Which was my point. In the absence of comparable data from motors driven straight off with no long warm-up, your oil analysis doesn’t really confirm things either way.
To rephrase your own assertion - “If you’ve ever tried to pour oil from a can at low temperatures, you’ll know exactly why you should reduce cold running to the absolute minimum.” Does that make sense?
newmercman:
Except that the forces are much lower at idle than they are at higher engine speeds, seeing as how the oil pump is gear driven and therefore pumps more oil as rpms increase.
That’s my answer to the question asked, if anybody wants to start up and go, that’s up to them, I’m just saying what I do with my engines. I’m convinced I’m doing it right and my oil analysis confirms that, I have very little wear metals in my samples (i drop the oil at 15,000miles in the CAT and 25,000 in the Volvo) and oxidation and nitration, which are indicators of excessive idling are at zero.
I don’t do it the other way to compare, so I can’t say one way is better than the other for certain, but my way works for me and as it all comes out of my pocket, it’s my choice to make.
Sent from my SM-G930W8 using Tapatalk
It doesn’t matter whether the forces (at the oil pump) are lower or higher - letting the engine warm up slowly means that it spends more time with cold, thick oil being pushed (slowly) through the bearings etc. Which was my point. In the absence of comparable data from motors driven straight off with no long warm-up, your oil analysis doesn’t really confirm things either way.
To rephrase your own assertion - “If you’ve ever tried to pour oil from a can at low temperatures, you’ll know exactly why you should reduce cold running to the absolute minimum.” Does that make sense?
As I said, my oil analysis is telling me that I’m doing it right, so don’t bother trying to convince me otherwise as you will be wasting your time. My engines, my money, my choice.
But to explain and put my quoted comment into context, pouring oil from a can in cold temperatures is like pouring treacle, my logic tells me that the kindest thing you can do to the engine is to let the pistons and bearings run at 700rpm rather than double that. And I have it in black and white that my theory is correct. The other way may work, I have no data to say one way or another is better, but I do know for sure that my way is a good way, you can disagree all you like, but I’m going to take the word of an oil analyst over the opinion of a ship’s captain or a lorry driver, no offence intended.
Rjan:
Cold engines also have looser tolerances, which is why the oil should be relatively thicker at cold than it would be with everything at operating temperature.
Just to correct myself, I’ve got this the wrong way around - no engine ever got tighter with heat applied!
But the principle still stands: that multi-viscosity oils are basically specified to be suited to the lubrication requirements of the engine both hot and cold.
Oil that is modestly thicker when cold does not necessarily starve any surfaces of lubrication.
Mass-production engines would not be designed nowadays with surfaces that couldn’t be lubricated for an appreciable number of minutes while the oil heated, because the amount of friction wear would be rampant.
To a point, thicker oil simply increases mechanical resistance (whist still providing adequate lubrication), which if anything generates heat and helps to warm the oil which can only be a desirable effect in this situation.
That is why the manufacturers advice is to give the oil a few seconds to circulate and pressurise, but no more.
Funny, if you ever read the handbook of an older Volvo lorry, it would advise running the engine warm before driving off.
Interesting how common turbo failures now are on lorries, as well as cars, interesting also to compare the drivers and vehicle that suffer from said failures.
Juddian:
Funny, if you ever read the handbook of an older Volvo lorry, it would advise running the engine warm before driving off.
Interesting how common turbo failures now are on lorries, as well as cars, interesting also to compare the drivers and vehicle that suffer from said failures.
Turbo failure occurs commonly because people DONT idle the engine prior to shut down.
Similarly to any turbine, a turbo needs to thermally stabilise prior to shut down and requires a cooling oil feed whilst doing so. If you motor a unit into the yard with any turbo boost then turn off engine, the turbo will not thermally stabilise. The rotor will drop from 120k plus rpm to 0 with the temp gradient falling out of control at the same time the oil flow ceases, the bearings overheat through the temp shock, baking the oil residue. You can crack turbine blades and housings this way and destroy the bearings. It only takes one bad hit. It’s alround bad juju on turbines/turbos.
I think on some road vehicles manufacturers build in oil supply systems that flow after shut down to mitigate bearing failure through bad practice.
Rjan:
Cold engines also have looser tolerances, which is why the oil should be relatively thicker at cold than it would be with everything at operating temperature.
Just to correct myself, I’ve got this the wrong way around - no engine ever got tighter with heat applied!
But the principle still stands: that multi-viscosity oils are basically specified to be suited to the lubrication requirements of the engine both hot and cold.
Oil that is modestly thicker when cold does not necessarily starve any surfaces of lubrication.
Mass-production engines would not be designed nowadays with surfaces that couldn’t be lubricated for an appreciable number of minutes while the oil heated, because the amount of friction wear would be rampant.
To a point, thicker oil simply increases mechanical resistance (whist still providing adequate lubrication), which if anything generates heat and helps to warm the oil which can only be a desirable effect in this situation.
That is why the manufacturers advice is to give the oil a few seconds to circulate and pressurise, but no more.
It’s clear that the least possible demand on the oil to seperate the moving parts of an engine is when it’s idling not under any load.Also bearing in mind that there is a difference between engine speed ( high idle ) as opposed to ‘load’.The oil cooler and water thermostats are what gets the engine up to temperature while a vehicle that isn’t moving obviously applies less cooling effect to the radiators as they open thereby providing a marginal reduction in the time needed to get the oil and water up to their optimum operating temps.Although having said that modern synthetic oil obviously changes things to a point but viscosity is still more about the fact that it needs to seperate fast moving parts under high load while providing optimum circulation at low temps.Bearing in mind that engine tolerances definitely close up at working temperature while synthetic oils can go up to 60 grade when hot.Which proves that they are designed to provide maximum protection at working temperature.IE putting an engine under any type of considerable load at low temperatures means that the oil will be at its weakest ( as low as 5-15 grade ) because at those temperatures it’s designed for circulation not protection.
As for supercharged piston aircraft.By FD’s logic they’d have just fired her up taxied out and took off ?.In which case I’d prefer nmm to be the pilot if we’re going out on a raid over Germany.While we’ll put you on the list as tail gunner so you’re as far away from the cockpit as possible.
newmercman:
If you’ve ever tried to pour oil from a can at low temperatures, you’ll know exactly why you should let it warm up before you force it around an engine.
It’s all counter intuitive in that we expect oil to be all thick and like tar at low temperatures which would probably be the case 'if it was single grade not multi grade let alone modern synthetics.In which case it’s optimum viscosity is when the engine is at optimum working temperature and all tolerances at their minimum.
IE it’s best to let the engine warm up under as little load as possible because at low temps the oil is designed for optimum circulation and optimum protection under load at working temperature.
