Once again about oil viscosity

Section Everything about SAE viscosity, article 7 of 7110 words, 1 minute

On oil viscosity being too high or too low

In this section: 7 articles
  1. What is oil viscosity? What it's for
  2. How to decode the viscosity index
  3. Which viscosity is better for the engine?
  4. Popular misconceptions about viscosity
  5. Viscosity value table
  6. What is oil viscosity? Myths and truth
  7. Once again about oil viscosity

On the site's forum, the same basic question comes up again and again: which viscosity of automotive oil is better to choose for different engines, and why official service centres sometimes fill something other than what's written in the owner's manual. Given how often these questions come up, it seemed to me worth returning to the topic of automotive oil viscosity once more.

Only this time let's approach it from the opposite direction and ask the question differently: what's worse for the engine — engine oil viscosity that's too high, or too low? And what happens inside the engine when the viscosity doesn't match the car manufacturer's requirements?

Question and answer

Read the whole “Everything about SAE viscosity” section