Engineering Explained made this cool video showing a car engine heating up through a Flir One thermal camera. Not to many surprises as to how the heat spreads, but it’s pretty cool to see the process.
Here’s the video descriptions for details on what equipment and car was used:
In this video we’re going to be cold starting the engine of my 2016 Subaru Crosstrek, and using a thermal camera we’re going to watch the engine heat up. The ambient temperature is about negative 6 degrees Celsius or about 22 degrees Fahrenheit. As far as metrics we’ll be monitoring, we’ve got overlays of the engine RPM, which will run higher when the engine first starts to help warm things up. We also have throttle position, the coolant and intake air temperatures, the temperature of where the thermal camera is centered, and a timestamp so we know how long the engine has been running.
If it’s freezing outside and you don’t want to get in a frozen car, no one’s going to fault you for warming up the engine and making sure it’s comfortable inside, as well as making sure the windows are defrosted so you’re ready to roll. In my video I was purely discussing what’s happening from a mechanical standpoint when you let your engine sit and idle.
Oil can actually flow at very low temperatures. You may be freezing, but for certain viscosity grades cold temperatures aren’t a huge deal. For example, my Honda S2000 recommends a 10W-30 oil, and it only recommends going down to a thinner 5W grade oil if ambient temperatures drop below minus 20 degrees C. Minus 20 degrees C! And this is logical based on SAE cold temperature viscosity ratings.
For example, a 0W oil needs to be able to pump at -40 degrees C. A 5W oil needs to be able to pump at -35 degrees C. A 10W oil needs to be able to flow at -30 degrees C, and so on. Oil can do a decent job of protecting your engine even at low temperatures, as long as you’re not asking the engine for too much power. Try to keep the revs low, and be light on the throttle until the engine is warmed up. Getting up to higher vehicle speeds is fine, as long as your acceleration is gentle and steady, and you’re mindful of your engine RPM. Source: http://www.viscopedia.com/viscosity-t…
Now inevitably someone in the comments is going to say they live in an area with negative 40 degrees C temps and they always warm there car up for several minutes before taking off. A couple of things to note here: first, that’s obviously super cold, and I can’t blame you for wanting the interior to be warm. Second, make sure you’re using a viscosity grade that can flow in these conditions. 0W is designed for this. Third, with temperatures this low, it’s a good idea to get an electric engine block heater so your engine won’t have to strain so hard to get oil flowing throughout.
At about 5 minutes and 20 seconds, when the coolant temperature reaches 50 degrees C, you’ll notice the engine RPM starts to significantly drop, eventually getting down to 800 RPM when the coolant reaches 60 degrees C.