Contour Enthusiasts Group Archives Forums General General Should I let the car warm up?

Originally posted by sigma:

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Originally posted by striker2:

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Originally posted by Rishodi:

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Originally posted by striker2:

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the best thing you can do is start it and drive. you actually wear off mor of the cylinder wall when the engine is cold than when its warm. the fastest way to warm it up is to drive it. however it takes the average car about 45 minutes to warm up.

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45 minutes? I don't think so!! It takes maybe 2 minutes for hot air to flow through my vents in the winter after starting my car up, and it can't take too long for the engine to reach its ideal temperature after that.

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the optimal operationg temp for an engine is about 210 degrees and it takes roughly 45 min to get there. the aluminium engines may warm up faster but our blocks are cast iron. when the engine is cold you actually wear about .008 off the cylinder wall for every hour idleing at that temp. you wear less than .002 off the walls when its at optimal operating temp.

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1> I don't see how those numbers could be correct. Using that math within a year of normal driving given what the average car sits at idle between traffic, start-up, and traffic lights, even at optimal temperature, an engine will have several mm of cylinder wear in just a year. There'd be no cylinders left after a couple years.

2> Assuming you're correct and that an engine at optimal temperature is 1/4th as harmful to the engine as one that's cold, why again would I want to just take off and drive?

For one, that relationship between 0.008 and 0.002 on the temperature curve would be non-linear, it would be a logarithmic curve of some sort. So, while it may take 45 minutes to fully warm an engine, that 0.008 done at "cold" is done right at startup and just a few moments thereafter. Cylinder wear would quickly decrease within a few moments to, let's say 0.004, then slowly decrease over the next 40+ minutes until reaching 0.002 in 45 minutes. Almost all of the period of high wear is done right at start-up.

So, in your rush to warm the motor 'because that does less wear', you drive it. Now, instead of having a cold motor sit at 750rpm doing 0.008 of damage, you're driving it and doing five times that because the cylinders are pumping 5 times faster in that initial time of high wear.

In those first few moments of high wear, you multipled the wear several times what it would have been sitting at idle. Those first few moments of high wear by revving a motor at its' 'weakest' will vastly offset the higher wear that one gets by bypassing that period of high wear, letting it pass at idle, then driving the car at a slightly cooler temperature at a point on the curve where wear difference really isn't that significant.

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