[JSeery]

I think the issue is GL5 is backward compatible with GL4, but this refers to the lubrication properties. Almost all GL5 containers state that it is compatible with GL4 applications, but it is NOT compatible with the "yellow" metal. You would have to know what additives they are using to assure "yellow" metal compatibility. Some even claim "yellow" metal friendly, but without knowing what they are putting in it there is really no way to know. To me it is not worth the chance when GL4 is available.