You’ve probably heard folks talking about the superiority of synthetic motor oil. You may even use it yourself—if you drive a newer high-performance car, it’s probably mandatory per the owner’s manual. But full-synth oil is one of those things that’s gone from smart car maintenance advice to car dad folklore. You know it’s the right thing to use, but maybe you don’t know why.
Thankfully, Engineering Explained’s Jason Fenske is here to help demystify the difference between conventional and synthetic motor oil, with a simple visual explanation that’s so brilliant, you’ll learn something even if you already know all the ins and outs of synthetic oil.
A big factor is viscosity, or how well the oil flows. Cold oil is thick, and it moves slowly (the animation above has been significantly speeded-up; the oil was chilled to -31 degrees Fahrenheit, and the used conventional oil was molasses-like in its slowness). That low-temperature flow problem gets worse and worse with every mile you put on your oil, so that by the end of your 5000-mile oil change interval, your oil behaves very differently than it does when new.
Go ahead, watch the whole video. Even if you already use synthetic oil religiously, and even if you understand everything about viscosity and temperature-dependent flow rates, you’ll still learn something.