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Originally Posted by landrovered
I think it is a case of "if the poison doesn't kill you the cancer will".
Wear occurs before the motor is warmed up at startup. We agree on that.
Cold oil is more viscous, I think we can agree on that.
The question is:
Which is worse for your engine, insufficient lubrication due to increased viscocity of cold oil, or the effects of inefficient combustion on your oil and catalytic convertor.
The lack of cars on the side of the road is not sufficient for me to change my views on this. The lack of evidence is not evidence to the contrary.
I have two cars that I have owned since new with over 200k miles on them on original engines.
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I'm not sure we do agree at all.
Wear occurs at startup - 85% in a 'normal' engine's lifetime. But not because the oil isn't warm, because all the floating parts - crank, cam aren't floating and because the other metal parts experience metal-to-metal contact until oil flows to float and/or coat or 'film' the other parts. It is quite literally akin to bearing starvation for a few seconds on each cold start. Bearing starvation on a track can destroy a bearing in just one turn, so you can imagine the cumulative effect this can have over time - it has nothing to do with the temperature/viscosity of the oil, only the absence of it.
And while cold oil may be more viscous, the question is more viscous than what? That same oil a few hundred degrees warmer? How much lack of viscosity is necessary for the oil to flow? What is the W on multi-grade oil mean? - That is the viscosity (or resistance to flow) of the oil at a certain temp - for a W0 rated oil, that temperature is: - 22°F and it's resistance is 3250cP. Compare that to a 25W oil which is 6000cP @ +23°F and you see what a tremendous difference it makes to use a multi-grade oil. And, in a multi-grade, this is the base oil - the addition of polymers means that the oil 'thickens' (in terms of resistance) as it's temp rises, not the other way round.
The question you pose isn't ąperpot. It isn't a question between these things at all. You either experience normal startup wear alone,... or you add to it the effects of inefficient combustion on your catalytic convertor and the adverse effects of reduced flow of coolant and oil to the engine - the first is unavoidable (unless you have an electric pre-luber), but the second is totally voluntary.
If you have cars with 200k on the original engines - congratulations! You fall into the group of about 75% of all people with cars built after 1994 - 200k is now the norm for modern engines which have been well maintained. That is not unusual at all these days.
Cheers!