I have always wondered about that. Thanks for the information.

On Sun, Oct 18, 2015 at 6:37 PM Tom Hargrave <thargrav@hiwaay.net> wrote:

> To be SAE rated all oils must be compatible. In other words, to be SAE
> rated you have to be able to add Brand B oil to brand A oil will no ill
> effects.
>
> Although this may not seem significant it really is. For any oil to mix
> with any oil with no ill effects means that their additive packages must be
> very similar!
>
> Jim
>
>