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Discussion Starter #1
I have a dispute with a friend that says that warming up the engine for more than two minutes will hurt the engine.

I know that in the manual tells you not to let your car warm up in the morning. But, I think it is to reduce pollution as the catalyst is not hot enough. Instead, to simply get in and drive.

I usually let me car warm up between 5-10 minutes when I have the time or I want to make sure the car is warm (specially inside).

My opinion is that today's vehicles are design to take a lot of stress in traffic, long running times, in very cold or hot weather. So I don't think warming the car up does any harm to the vehicle...

Specially when you consider all the stress conditions that vehicles go through...

What do you think?
 

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In my experience warming up the car for over 5 mins does not hurt the engine. I have a 94 pathfinder with 123,000 miles on it and still running great and I usually warm up this car for over 10 mins everyday. To me this probably prolong the life of my pathfinder. I'm doing the same thing for my X and it's not hurting anything.
 

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I think it's a probably a complete waste of gas. Also, the car is polluting almost as much at idle as it would be if you were just driving it - particularly because it takes so much longer for an idling engine to warm up compared to one that is being driven. (For idling let's arbitrarily say that it's 10 minutes polluting an an average rate of "10 units/minite" when warmed up idling, followed by 15 minutes of commuting at an average rate of "2/min". For just starting up and driving, let's say 15 minutes at an average rate of 10/min (maybe 20/min at the start of the trip, and the same 2/min as above by the end of the 15 min trip, for an avg. of, say 10/min. So, using these numbers, admittedly made up, but probably not that far off:

Idling followed by trip, total pollution is 10 x 10 plus 15 x 2 equals 130 pollution units.

No idling, 15 min times 10/min equals 150 pollution units.

Hmmm. based on my made up numbers, I just showed your method might pollute less. (But I think it would use more gas - you could find out for yourself with your mpg gauge). Plus there's the big problem with my calculations above of my numbers being all made up. If reality were only a little different, the results could reverse.

But in any case it shouldn't hurt the engine.
 

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Just run it until it idles smoothly and go. Save the gas.
 

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I read somewhere years ago that a high percentage (something like 80-90) of engine wear occurs in the first few minutes after starting.

When I first start up the MDX in the morning I will drive out of the garage immediately but I keep the RPM's under 2000 for the first few minutes.

If it is parked outside and the temp is low I will let it idle for a few minutes before driving, then keep the RPM's below 2000 until the temp gage indicates that it has warmed up.
 

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BaldEagle said:
I read somewhere years ago that a high percentage (something like 80-90) of engine wear occurs in the first few minutes after starting.

When I first start up the MDX in the morning I will drive out of the garage immediately but I keep the RPM's under 2000 for the first few minutes.

If it is parked outside and the temp is low I will let it idle for a few minutes before driving, then keep the RPM's below 2000 until the temp gage indicates that it has warmed up.

Thats a good idea becasue it also lets your tranny warm up.
 

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Idling warm up is not required in today's fuel injected engines. In the old days, engines with carburetors can run erratically if it has not been warmed up sufficiently because fuel metering chokes in them were extremely temperature sensitive. Plus the old venturi effect in the carburetor would not vaporize the gasoline and mix with the air properly when the engine is cold, and hence poor engine performance. Therefore, warm up was virtue in a carbureted engine. This is the old school of practice. People coming from the old school are still applying this method to the modern engines. That is wrong. Today's fuel injected engines avoid all the mechanical stuff in a carburetor and therefore drivability does not affect by the temperature. Theoretically, it means you could start up you car and drive it right away. In reality, you should always let the engine idle 30 seconds to a minute so that electronic components in the control circuits have ample time to stabilize themselves. This is analogues to the engine warm up virtue. Things work better when warm, electronic devices are no exception. After the short idle, you should drive on and drive gently for a mile or two. Gently means light-footed. If you jab your gas peddle heavily during this period, you are virtually shortening your engine's life by the mile of thousands because the chance of metal to metal rubbing is at its highest when the engine is cold. It will cost you dearly. That is why the car guys always say don't race your engine when cold. If it is so unsafe, why don't we just let the car warm up idly? The reason is because idling causes much more pollution than driving. In today's car, the main device for reducing exhaust emissions is called catalytic converter. Without it, our world would have been a very different place. Catalytic converter is a wonder device when it is lighted up because it will convert harmful gases into good gases (not poison gases) indefinitely. However, it is nothing but a pile of glass pellets stocked in your exhaust pipe when it is lighted off. It has no affect on harmful gases from the engine. The catalytic converter is in the light-off state when the engine is just started and before it reaches the normal operating temperature. The converter has to absorb so much heat energy from the exhaust gas before it can be lighted up. In order to hasten the light-up process, more and hotter exhaust gas is needed. To do that, the engine must be loaded. To load an engine means it must be driven. Driving will get you a lot of hot gas in a very short period of time while it will take a long long time for idling to achieve the same. No only idling takes long time to heat up the catalytic converter, it also takes the same amount of time to pollute the environment while it is trying to light up the converter. So think again next time when you try to warm up that car on your driveway. To keep the world clean, or at least not choking to death, every little effort helps. If you are an owner of a MDX, you have already made your contribution to the world because it has two cascaded catalytic converters. One of them is placed at the exhaust manifold where the exhaust gas temperature is hottest. You guessed, it will light up much faster than any other converters out there because conventional converters are usually placed somewhere on the bottom of cars. This also translated into lower exhaust gas emission. That is why HONDA claims itself an ultra low emission vehicle manufacture. I hope this clarify things.
 

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Kucat-
Nice explanation, thanks. Interesting stuff...:)
 

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DaleMDX and kucat have it well nailed down IMHO. It is important to warm up all lubricated system from the engine through the drive train, to the wheel bearings, gently before driving it at normal speeds. Idling does nothing to help that.
The 30 second rule is a good one for stablization..and others may want to extend that a couple of minutes for extreme low temps.
But driving it gently until the temp gets of the peg into the normal range is always a good thing to do.
 

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So I shouldn't keep practicing my 10 minute warm-up schedules in the mornings because my MDX is polluting the environment?:confused: The MDX is so technologically advanced that all it requires is a quick 1 minute warm up for the engine to reach safe driving temperatures?

Personally I was totally blind to the environmental factor, I just figured (as a precautionary thing) to let the car idle in the morning until the tach needle was below 1,000 rpm's. The MDX, after been driven, idles at 500-800 rpm's when in [P]. I just guessed that the engine is warmed up when it idles at those rpm's.
 

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DaleB said:
DaleMDX and kucat have it well nailed down IMHO. It is important to warm up all lubricated system from the engine through the drive train, to the wheel bearings, gently before driving it at normal speeds. Idling does nothing to help that.
The 30 second rule is a good one for stablization..and others may want to extend that a couple of minutes for extreme low temps.
But driving it gently until the temp gets of the peg into the normal range is always a good thing to do.
:werd:

We idle for 30 secs (max) then hit the road, gently til it's up to temp -- usually within a few minutes.

Peeps in colder climates YMMV of course. Might let it idle a bit longer before hitting the road. Defrosting windows/heating the interior, etc might be needed, too. But if it's warm enough for you and the windows are clear, IMO a minute or two of idling before hitting the road is plenty.

And don't idle in the garage with the windoze down and/or the garage door closed :)
 

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Discussion Starter #12
Thanks everyone for your responses... :29:

What I gather is that warming up the engine a few minutes does not hurt the engine BUT

- Increases pollution
- Wastes gas

It helps though in...

- Lets oil circulate before placing a load on the engine
- Electronics Stabilized
- Warms/Cools the interior

Did I miss anything? :confused:
 

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People, there is NO NEED to idle even for a few seconds. Just fire her up and go! The ONE THING that you MUST religiously adhere to is: NO HARD DRIVING until the temp needle reaches its normal point (when fully warmed up, on our cars I think it's like a little less than 1/2 way). If you stick to that rule, you will see a very, very long life for your engine (and probably other moving parts).
 

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ndahbar said:
People, there is NO NEED to idle even for a few seconds. Just fire her up and go!
I disagree. I read a CR article on prolonging engine life a few years back. It stated that in warm weather 15 secs of idling is plenty. In cold weather, 30 secs is sufficient. Again, it is important to drive gently until oil reached the DOHC(the top of the engine), but excess idling destroys the environment, and may cause more engine damage.

basically, I advised my wife to wait unitl the Navi screen shows the disclaimer before getting out of park. I calculated that it takes 14-15 secs to get to that screen.
 

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Discussion Starter #16
MDXLuvr said:


...but excess idling destroys the environment, and may cause more engine damage.

How does it caused damage to the engine?
:confused:

That is the question...

The engine does not know whether the vehicle is moving or not... the pistons move up and down just the same.... and if we are talking about letting the engine reach operating temperature slowly what is the difference? (besides the important factor on environment and waste of gas).

My debate with my friend is whether it causes damage to the engine or not.... Not whether is the right thing to do...

I guess We are looking for a more precise explanation on how warming up the engine damages the engine...

Thanks for your feedback... :)
 

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ndahbar said:
People, there is NO NEED to idle even for a few seconds. Just fire her up and go! The ONE THING that you MUST religiously adhere to is: NO HARD DRIVING until the temp needle reaches its normal point (when fully warmed up, on our cars I think it's like a little less than 1/2 way). If you stick to that rule, you will see a very, very long life for your engine (and probably other moving parts).
I agree except if it has been parked outside in below freezing weather. Then you need to let it warm up till the defrosters start working for safety considerations.
 
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