Jason S8

..when warming up from cold? This appears to be the accepted 'wisdom', but surely driving the car produces more wear on the engine when cold and when the oil has not had a chance to reach all moving parts.

Why should an idling engine cause more damage?

ryoung

... when the motor would normally idle very rich on a cold start-up?

I believe the concern was that you get liquid gasoline washing oil off the cylinder walls, with excessive ring and cylinder wall wear the result. I tend to agree that this may not be a problem with today's sophisticated fuel injected motors.

But before I stick my neck out too far on a lubrication issue -- Kjell, your opinion?

Jeremica

The manuals on all my BMW's (740iL & M3) are very clear that the manufacturer recommends driving away immediately after starting the engine and NOT waiting for it to come up to operating temperature before driving away. The manual recommends keeping the RPM's low until until everything has come up to temperature. Modern synthetic oils do a pretty phenomenal job of coating engine parts to prevent damage in the first few minutes of operation. I'm not sure why idling for prolonged periods of time is so bad...

Wilfred

both oil and water temperature have stabilized at their norm before driving regularly. Until then, I start off immediately, but drive like I'm an airplane pilot taxiing around the runway...slow acceleration, no downshifting, nothing stressful.

KjellA

I believe the reason not to let it idle from cold to working temperature is that it will build up more acid gases when slowly warming up, and that the oil pressure and flow is to low to transport these gases away at idle.

This section is taken from Chris Longhurst's "The Engine Oil Bible" at
http://www.fernblatt.com/longhurst/engineoil_bible.html

I think what Chris writes here makes perfectly good sense:

"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. "

Seattle Scott

Flow would be the parameter that was reduced if the oil pump can't deliver the needed volume. Right? Pressure is created when there is resistance to flow, cold, thick oil offers more resistance to flow.

I think you got the major point, you need to warm up the engine quickly so the combustion process is more efficient but starting and going to high RPMs is bad. Don't forget higher carbon buildup when gasoline engines are cold or idling.

The fastest way to warm up the engine is to put it under load, i.e. drive the car.

I let the car idle for 30-60 seconds before putting the transmission in gear and TRY not to go over 3000 RPM (an old V6 2.8 liter 12 valve engine) until the oil temperature is nominal.

I understand running a rich fuel mixture, i.e. a cold engine, is also bad for the 02 sensors so extra air is pumped into the exhaust manifold.

Seattle Scott

You think that angle of attack might have more to do with carb icing than manual chokes????

KjellA

Right, it has to be flow, not pressure (when cold)

nick n

..is not burning at a high enough temperature resulting in those notorious carbon deposits. The car would have to be idled habitually in order for problems to come about. -Just something else to watch out for.

For those that remember, we're still looking for an A8. I came across a sharp 99' pearl A8q with low miles (don't recall exact mileage) but it didn't have some of the features that were were looking for - still playing it by ear.