A few interesting facts about oil viscosity

Choosing an automotive oil needs to be approached very responsibly. The longevity of your vehicle's mechanisms depends on the product you buy. Every car owner ends up with questions about oil viscosity that they can't always answer on their own.

First of all, it's worth recalling what viscosity actually means. It's the ability to remain fluid while still staying on the surface of engine parts. Among car owners, there are two mistaken beliefs that lead to serious breakdowns. Many are convinced that a sportier oil suits fast driving better, and use that kind of oil accordingly.

The result is that wear on the mechanisms increases many times over. The second mistaken belief is that even old engines need the most modern oils. Car owners assume that the manufacturer of an old car simply couldn't have recommended the newer formulations, since they didn't exist yet. In reality, old engines aren't designed to use the newest oils either, and that inevitably leads to breakdowns.

So how do you correctly choose the right viscosity? Let's repeat once more: you need to choose an oil with the viscosity specified by the car's manufacturer. Otherwise, you'll lose engine power and accelerate its wear. Mopar ATF+4 fluid, and any engine oil for that matter, is chosen on this same principle. So what happens if the oil's viscosity is too low or too high, and which is worse?

To answer that, it's worth recalling the clearances in friction pairs. The diameter of the piston assembly with its rings needs to be slightly smaller than the cylinder's internal diameter, otherwise the mechanism simply won't work. Engineers design the clearance to match a specific thickness of the oil film coating the mechanism's parts. In that case, you get the maximum possible power for that engine.

As oil viscosity changes, engine power decreases or increases. If viscosity is high, the clearance in the friction pair shrinks, and engine power drops. At the same time, when the engine starts, friction forces increase, and temperature in the system rises sharply. So, high viscosity means a faster warm-up, but in severe frost it shortens the engine's service life by 300-500 kilometres. Low engine oil viscosity means a slower warm-up, but a longer service life for the mechanism. So the choice is yours.