Letting engine idle a bit on startup = good!

[Interceptor]

From Bob is the oil guy site:

The current trend is the "90% of your engine wear happens at startup" advertising ploy. This fact is absolutely true, but as it happens, it's less to to with "grinding engine parts" and more to do with combustion. When the combustion gases burn, they form acids which are highly corrosive when their vapours condense. These acids collect in the upper cylinder areas where their temperature is raised above their dew point. The acids condense and etch the cylinder walls and piston rings. In reality, this accounts for over 85% of engine wear, the other 15% being down to abrasion. So the adverts are nearly right - most of the engine wear does happen at startup, and it is because of a lack of oil, but it isn't because the oil isn't coating moving parts - it's because it's not transporting these acidic gases away. Having said that, if you start the engine and let it idle for 15 seconds or so before moving off, you can probably add another 100,000 miles to your engine's life without one bottle of additive. This warms the oil up a tad and makes sure it's in all the most vital areas before you start putting a strain on the engine. Most handbooks tell you not to let the engine warm up before driving off (they're referring to the acid corrosion mentioned above), but they mean don't let it reach working temperature. If, however, you insist on starting up and belting off down the road, think of this next time: it takes an average engine around 3 minutes of average driving for the exhaust manifold to reach 300°C. If you blast off and run around at full throttle, right from the word go, that process takes a little under a minute. Think about it - from outside air temperature to 300°C in a minute - what exactly is that doing to the metal in your manifold? Ask anyone who's ever owned an original Audi Quattro - they'll tell you exactly what happens.

[DanDombrowski]

These acids collect in the upper cylinder areas where their temperature is raised above their dew point. The acids condense and etch the cylinder walls and piston rings.

Either they have that backwards, or its just wrong. If a gas is raised above its dew point temp (or more correctly across the gas/liquid phase line for that pressure), it will stay a gas (or go from a liquid to a gas). If you want to condense the gas, you have to lower the temp below the 'dew point'. Or just raise the pressure.

[granit_silber]

Either they have that backwards, or its just wrong. If a gas is raised above its dew point temp (or more correctly across the gas/liquid phase line for that pressure), it will stay a gas (or go from a liquid to a gas). If you want to condense the gas, you have to lower the temp below the 'dew point'. Or just raise the pressure.

Isn't the upper cylinder area where the fuel/Air mixture is compressed before ignition? (not being a jerk, just unsure about the terminology)
-ashley

[DanDombrowski]

Yes, it is, the fuel/air is compressed in the upper portion right before ignition. However, they're talking about combustion gasses.

I think what they're trying to say is that if the oil isn't warmed up, the top of the cylinder head is cold, and the gases are lowered below their condensation temp, and then they condense into liquid on the cylinder head walls.

[bahnstormer]

Yes, it is, the fuel/air is compressed in the upper portion right before ignition. However, they're talking about combustion gasses.

I think what they're trying to say is that if the oil isn't warmed up, the top of the cylinder head is cold, and the gases are lowered below their condensation temp, and then they condense into liquid on the cylinder head walls.

clearly 15 seconds of warm is fine...

the origanal arguement stems from those people that
idle the car until teh coolant temp is at 12 oclock
which does not warm the car's oil, or other liquids such
as tranny fluid, diff oil etc

this is an ideal warmup procedure

turn on motor
fasten seat belt
turn on and tune radio
check mirrors and the like
turn on lights

engage first and drive with rpm's below 3k for some time
that last some time part depends on weather conditions and
engine oil temps

[SRR2]

The sound of this makes me think of advertisements for things like magnetic fuel line add-ons that supposedly raise your fuel mileage. I mean, really, 15 seconds of idling will add 100,000 miles to your engine's life. Uh, sure. Their fundamental misuse/misconception of "dew point" damages their credibility too.

I think we can all agree on bahnstormer's post.

[Robin-535im]

How can I not post to this one?

I recorded how long it takes to warm up at idle and while driving around. The difference is about 2 minutes if you a) idle until water temp at 12 o'clock vs. b) drive immediately and keep rpm's around 2000 RPM until temp at 12 o'clock.

If you multiply the warm-up time by the RPM, you find out that it takes roughly the same number of engine rotations to get to operating temp no matter if you idle or drive. I.e., you need 15,000 cylinders to fire to reach operating temp no matter what.

That tells me that each little explosion adds an equivalent increment of heat, (and a given increment of wear too).

Engine engineers surely know more than I do about the process, but so far I see no good reason to justify driving off immediately. Still looks like a wash as far as I can see.

I suspect wear is primarily a function of work done by the engine and number of rotations done... the best way to increase life of your engine is to not load it much and not rev it much... but what fun is that?

[High Compression II]

You are not taking into account, the QUANTITY of gas/air burned. The more in a given time = greater heating effect!
Therefore, if you drive off and floor it from cold, it WILL warm up faster, but for other reasons this is not advisable!

Probably takes MORE than 15 seconds for oil to properly lubricate the pistons rings bores etc, which relies mainly from splash from the crank, and oil emitting from the bearing journals When the oil is cold and reluctant to move, it could be much longer..........

The cylinder bores do not have their own oil supply remember, but rely on mist and splash derived from the bottom end. Both not present in the first few seconds of running!

The oil jets under the pistons on some engines arn't for lubrication--They are for cooling, and directed at the piston crown underside, and dont hit the bore walls.

[pundit]

Basically it takes me about 30 sec after I start, seatbelt, radio, slow reversing etc. before I begin to drive off. Then I don't exceed about 2000 rpm until the temp gauge hits about 1/4. Even then I barely get over 3000 rpm on my way to work. With modern more free flowing oils extended idling warm up periods are less of a requirement. I agree one shouldn't subject the engine to excessive revs or load for the first few minutes... but I don't.