Comments by "" (@tomk3732) on "Will Thin Motor Oil Cause Engine Damage? Let's Settle This!" video.

  1. The 2nd number is working viscosity. The first is cold viscosity. The 2nd should not vary from what manufacturer recommends. The first can, for example, with recommended 5w-30, it is totally safe to use, and better in winter, 0w-30. You can use something like 10w-30 in spring. Or straight 30 in summer. When requested, manufacturer will provide whole table of oil to cold start recommendations. To thin oil, 2nd number may cause wear by not sticking enough while to high number does opposite. There is always big discussion of oil for use in machinery. Hunting for strange oils, like ISO 18 for my Lathe or ISO 10 for surface grinder. Note different viscosity scale.
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