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Just thought I’d throw this out there….. Seems a LOT of people think that cold start extended idling somehow prematurely “damages” an engine. I have no idea why this myth persists as it’s clearly incorrect. Maybe because the vast majority didn’t do physics at school. Who knows?
Anyway. The fact. (And for simplicity reasons I’m using fuel injection and ECU enrichment assisted engines) Cold start extended idling does NOT prematurely wear out an engine. The “myth” revolves around the erroneous assumption that the enrichment process required to start a cold engine is running the ENTIRE time the engine is idling. This is of course absurd. A richer mixture is dependent upon the ambient temp & engine block temp. As soon as the engine is started the ECU amongst many functions provides a richer fuel mixture until certain temp parameters are met…. In most modern engines I find them leaned out to almost normal op mixture after 5-10 minutes or 45-50 degrees celcius is reached. A simple test is that one can’t “smell” that gasoline odour after 5-10 minutes.
So it’s quite simple. You will NOT prematurely harm the engine by starting it up then say going inside & waiting for the engine to come up to temp before driving off. You WILL of course use more fuel due to the fact that you are not covering any miles whilst the engine warms up. I see statements in forums all the time like “Oh yes, the quicker you can start up and go the faster the engine will warm up as it’s under load from acceleration” Blah blah blah! Total nonsense. A cold engine will in fact warm up FASTER if left stationary as the heat builds up in the engine bay without any frontal cold air flow that would be caused as the vehicle is driven at speed.
And finally for those that either can’t understand or don’t want to change their long held beliefs, just realize one thing. Cold starting is causing MOST of your engine wear regardless of extended idling or start and go. The best example of this is a taxi cab. At least in Australia the cabs are swapped at shifts and are only switched off to refuel. The average cab life here in miles? Try 500,000+ Reason? Apart from obvious regular oil changes and servicing, THEY ARE ALMOST ALWAYS AT correct hot engine operating temp which unlike the average car that goes through thousands or tens of thousands of cold lube starts, these cabs have greatly reduced engine wear.
Hope this helps. Extended warm up will use more fuel granted but it is NOT anymore chronically causative of “fuel dilution of engine oil” etc etc as most seem to think. There are several other causes for fuel dilution. In a nut shell: The ECU is automatically leaning the enrichment process on a temp sensor basis which obviously is also therefore based on time elapsed.
Cheers from Australia!
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OH JUST TO ADD….. THIS FROM WIKIPEDIA…… TYPICAL NONSENSE!
Myth: cars need to idle to warm up the engine. Reality: the engine warms up faster when being driven.
OK. I’VE HAD ENOUGH OF THIS BS! YES if you cold start an engine then take off immediately using maximum redline revs it will certainly get warm fairly darn quick! But then how much premature engine wear would THIS cause!? LOL
Funny.
The way I always heard it dealt with, is that people often say you HAVE to let a vehicle warm all the way up before driving. Yeah there is no damage in idling, a engine really does not care one way or another, running is running. Used to be once diesels were started they were rarely ever shut down, now most companies have a idle limiter installed that shuts down the motor if it is left idling too long to save fuel.
[quote=”Raistian77″ post=82948]Funny.
The way I always heard it dealt with, is that people often say you HAVE to let a vehicle warm all the way up before driving. Yeah there is no damage in idling, a engine really does not care one way or another, running is running. Used to be once diesels were started they were rarely ever shut down, now most companies have a idle limiter installed that shuts down the motor if it is left idling too long to save fuel.[/quote]
Yeh I hear yah! To me it’s the cold starts that takes the toll. But yes the fuel saving I understand. IMHO, I’d rather pay a few bucks more a week and have a healthier engine. Oh and I’m NOT advocating that extended cold OR hot idling is a GREAT thing emissions wise just that my critics claim cold start extended idling creates more fuel dilution of oil compared to start and go. I don’t buy it. Particularly given the fact that we now have computers running the enrichment process versus one’s hand and a choke lever/cable.
[quote=”ojdude” post=82953][quote=”Raistian77″ post=82948]Funny.
The way I always heard it dealt with, is that people often say you HAVE to let a vehicle warm all the way up before driving. Yeah there is no damage in idling, a engine really does not care one way or another, running is running. Used to be once diesels were started they were rarely ever shut down, now most companies have a idle limiter installed that shuts down the motor if it is left idling too long to save fuel.[/quote]
Yeh I hear yah! To me it’s the cold starts that takes the toll. But yes the fuel saving I understand. IMHO, I’d rather pay a few bucks more a week and have a healthier engine. Oh and I’m NOT advocating that extended cold OR hot idling is a GREAT thing emissions wise just that my critics claim cold start extended idling creates more fuel dilution of oil compared to start and go. I don’t buy it. Particularly given the fact that we now have computers running the enrichment process versus one’s hand and a choke lever/cable.[/quote]
I agree, maybe back when manual chokes were in use I would agree, but modern computer controlled engines? not likely.
[quote=”Raistian77″ post=82957][quote=”ojdude” post=82953][quote=”Raistian77″ post=82948]Funny.
The way I always heard it dealt with, is that people often say you HAVE to let a vehicle warm all the way up before driving. Yeah there is no damage in idling, a engine really does not care one way or another, running is running. Used to be once diesels were started they were rarely ever shut down, now most companies have a idle limiter installed that shuts down the motor if it is left idling too long to save fuel.[/quote]
Yeh I hear yah! To me it’s the cold starts that takes the toll. But yes the fuel saving I understand. IMHO, I’d rather pay a few bucks more a week and have a healthier engine. Oh and I’m NOT advocating that extended cold OR hot idling is a GREAT thing emissions wise just that my critics claim cold start extended idling creates more fuel dilution of oil compared to start and go. I don’t buy it. Particularly given the fact that we now have computers running the enrichment process versus one’s hand and a choke lever/cable.[/quote]
I agree, maybe back when manual chokes were in use I would agree, but modern computer controlled engines? not likely.[/quote]
True that! But. Well……. If you want to be truly horrified. Guess what car manufacturer has a big problem dealing with interval service fuel dilution of engine oil? One hint. They are made in Italy and are VERY expensive! LOL
Hmmm I have some disagreement with the OP. Extended idling can lead to a phenomena known as bore wash. Most owners handbooks tell you not to warm the car up from cold, but to start driving immediately. Engineers wrote those books and would’ve put that in for a reason.
However that said, the main worry I would have for the scenario given by the OP is that my car might be stolen whilst I was inside waiting for the car to warm up.
I think the advice of not allowing an extended warmup is promulgated by EPA due to emissions. Driving the vehicle apparently gets the catalytic convertor to operating temperature sooner than idling.
Now, if you live one block from the freeway this may not be good advice. Some modern engines can produce amazingly high oil pressure when cold and with the crummy construction of most oil filters you chance popping the filter.
[quote=”cjmillsnun” post=83097]Hmmm I have some disagreement with the OP. Extended idling can lead to a phenomena known as bore wash. Most owners handbooks tell you not to warm the car up from cold, but to start driving immediately. Engineers wrote those books and would’ve put that in for a reason.
However that said, the main worry I would have for the scenario given by the OP is that my car might be stolen whilst I was inside waiting for the car to warm up.[/quote]
As I mentioned. The ECU controls the enrichment process which is temp dependent & hence “time” dependent. There is a persistent myth whereby people erroneously believe the the ECU is running high enrichment the entire time an engine is idling cold OR HOT which is simply not true. I can’t imagine ANY engineer adhering to something which is simply illogical. And FYI my owners manuals for cars and bikes we own say “not extended idling when HOT”. A weird thing to say as one can only imagine how many tens or hundreds of millions of engines are idling for hours in traffic all over the world.
As an adjunct. My elderly father still has his car bought new in 1971 and it’s now covered 455,000 miles and he NEVER EVER didn’t idle that engine for a good ten minutes every time he drove it. And this is a NON ECU vehicle! It’s never even had the head off and compression is still good. Oil & filter change every 5,000 miles. That’s good enough for me. Borewash is almost always caused by fuel blowing by the rings as a result of A: Plain wear. Or B: Engine was babied during run in procedure from new.
[quote=”barneyb” post=83106]I think the advice of not allowing an extended warmup is promulgated by EPA due to emissions. Driving the vehicle apparently gets the catalytic convertor to operating temperature sooner than idling.
Now, if you live one block from the freeway this may not be good advice. Some modern engines can produce amazingly high oil pressure when cold and with the crummy construction of most oil filters you chance popping the filter.[/quote]
YES exactly! Of course the EPA are correct. I never said extended cold idling didn’t use more gas. Obviously it does as the vehicle isn’t going anywhere for several minutes. I’ve started my bikes and felt the cat box with my bare hands and trust me it gets HOT very VERY quick! Also. It isn’t so much the cold oil producing higher pressures. Rather it’s the fact that cold/thicker oil doesn’t provide that thin warmed up film engines crave. I’ve never seen an engine fail due to too thin an oil (excluding engine flush oils!) But. Too thick a viscosity? Oh yes! Why do you think we have multi viscosity oils nowadays? Try running an SAE W30. LOL
[quote=”cjmillsnun” post=83097]
However that said, the main worry I would have for the scenario given by the OP is that my car might be stolen whilst I was inside waiting for the car to warm up.[/quote]
Well I live in the mountains of Australia on a large property. We don’t have any crime to speak of here you could say as there is no one around. But yes I do get your point if you live in an urban environment.
Well..here is my 2 cents worth. I have been driving for 40 plus years and repairing them for 45 plus years and I think with older carburetted cars there was a definite negative to cold idling, especially in very cold climates. In those days we mostly had 10w30 motor oils that were like molasses when cold. Do you think that molasses was getting thrown on the cylinder walls and camshaft at idle at -18c (0f)? I saw many camshaft and rocker arm failures in those years. I questioned customers who had these problems about cold idling and most said that they did that.
Now that we have fuel injected engines and 5w30, 5w20 and 0w20 oils as well as synthetics and the fact that they mostly have roller lifters and rocker arms that don’t need as much lubrication to survive as well as anti scuff coated piston skirts, I believe that cold idling is not as critical today. They also have better control over fueling.
That said, I can idle my 07 Dodge Caravan 3.3 for 15 min. at -18c and it’s only partially heated up but if I drive it it’s warmed to operating temp in 10 min. I have proven that to myself.
[quote=”wysetech” post=83633]
That said, I can idle my 07 Dodge Caravan 3.3 for 15 min. at -18c and it’s only partially heated up but if I drive it it’s warmed to operating temp in 10 min. I have proven that to myself.[/quote]
Don’t know why that would be. Unless you are placing the engine under a fairly decent load whilst cold??? But FWIW, NA aircraft are all idled prior to take off. Standard procedure. After starting engines, idle them at 800 RPM’s until the oil pressure becomes normal, then increase to 1100 until taxi time. This will prevent “loading-up.” To prevent engine damage due to cold oil, DO NOT EXCEED 1100 RPM’s until the oil temperature is 55 degrees Celsius. Do not close cowl flaps to heat engines up in a hurry; this causes unequal cylinder temperature. Usually there will be ample time for engine warm-up before take-off. In any event, don’t take off until engines are warmed-up. To assure proper cooling, “ground run” engines in “auto-rich” and, if possible, head the aircraft into the wind.
On the older FI cars/trucks the O2 sensor was a single wire unit with no heater. Extended idling could cool the manifold down enough the O2 would quit working and make the vehicle enter “open loop”. Open loop causes the engine to use more fuel than closed loop does so the EPA pushed hard for people not to idle their vehicles. Now the O2 sensors have their own heaters and usually do not drop out into open loop when idling anymore.
[quote=”Raistian77″ post=83679]On the older FI cars/trucks the O2 sensor was a single wire unit with no heater. Extended idling could cool the manifold down enough the O2 would quit working and make the vehicle enter “open loop”. Open loop causes the engine to use more fuel than closed loop does so the EPA pushed hard for people not to idle their vehicles. Now the O2 sensors have their own heaters and usually do not drop out into open loop when idling anymore.[/quote]
Exactly! I should have qualified this topic by stating I was in no way referring to non EFI or “older” technology. But to re iterate if extended idling is SO BAD for an engine tell me why cabs etc will easily get 500,000 miles on them and still have a quite decent engine life left. And most cabs I’ve seen spend a LOT of time idling!!!! In Australia at least I’ve never seen one switched off. Also the tens (hundreds) of millions of vehicles stuck in traffic jams the world over must be expiring at an alarming rate due to extended idling now wouldn’t they? LOL
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