It’s that time of year again, and there are numerous articles out there about the subject of warming up a car when it’s cold outside before driving off. Thanks to changes in technology, oil, tolerances, fuel injection, electronic engine controls and manufacturer’s recommendations, the mantra for some time is to just drive off, gently for the first couple of minutes, as there’s supposedly nothing to be gained by letting an engine slowly warm up at idle speed. So I was a bit surprised to run into an article promoting a pre-drive warm up.
I happened to check in at Jalopnik the other day, and ran into Jason Torchinsky’s post promoting a pre-drive warm-up. Here’s his main point:
The reason has nothing to do with fuel or my latent desire to pollute your driveways — it has to do with oil. When your car has been sitting out overnight, all the lubricating oil that’s coating all of the crucial, moving bits of the car has settled down to the bottom of the oil pan. When the temperatures are really cold, not only is that oil not near the areas it needs to be, its viscosity — ability to flow — has been severely impaired by the cold. You’ve seen how differently, say, refrigerated maple syrup flows compared to hot syrup — the oil is the same way.
So, when you start that cold engine, it’s essentially running without lubrication. If you start up and immediately put a load on the engine, things could get damaged. It’s just not ready to go. Take a minute or two to get that oil pumping around before putting any load on the engine, and your pistons and camshafts and turbos and other spinning, moving bits will be much, much happier.
Now, you don’t need to idle for a half hour, but a few minutes just to get the fluids a bit thawed out is not a bad idea at all. Have a stick shift? Have you ever felt how sluggish the stick feels on a really cold morning? Think about all the components inside that housing, and how they’re doing. Let the car have a moment to wake up and spread some warmth and fluids around.
Frankly, there’s no harm in a short warm up, but his point about the oil and lack of lubrication is not really accurate. Oil pressure builds almost instantaneously, and oil is essentially non-compressible, which means that the positive displacement oil pump will pump the same amount of oil regardless of how cold it is. And if one is using the appropriate oil, it’s not likely going to have the consistency of refrigerated maple syrup. And for what it’s worth, cold oil has better film strength than warm oil.
I’ve been long convinced that driving off reasonably gently is no different to a cold engine than sitting idling. And it will warm up the engine faster. And the transmission isn’t going to warm up while sitting idling anyway, unlike Torchinsky claims. But when it comes to issues like this, everyone has an opinion. What’s yours?