5W-50 or 0W-30?
Or which is worse for the engine, viscosity that's too high or too low?
In this section: 6 articles
It might seem that everything about the viscosity of engine oils has already been chewed over, but apparently not quite. The questions that keep coming up on the site's forum suggest there's still more to say on the subject of oil viscosity. So, which is better to choose, a higher or a lower engine oil viscosity? And what should you do if the warranty service fills your car with an oil whose viscosity isn't the one specified in the owner's manual?
Let me say it once again straight away: your car's oil viscosity has to match the manufacturer's requirements, regardless of the car's age, mileage, driving style, budget, or the "authoritative" opinion of service technicians, even at an official dealer. This article is written for those who have doubts, and for those who are simply curious why that is. If that's you, read on; if not, read the owner's manual (or the service book), and insist that you're only ever given the engine oil specified by the engine's designers, in every respect, viscosity included.
So, let's dig into the question of engine oil viscosity. The friction pair in the engine that's easiest for most drivers to picture is the "piston-cylinder" pair, so for the sake of clarity we'll use that very pair in our little logical exercise.