"I suspect our staff is mixing lubricants before they are even used. Is there a simple way to determine this?" Unfortunately, there is not an easy way to tell if lubricants have been mixed unless they have vastly different viscosities, such as ISO 32 and ISO 680. You then most likely would see a thickening or thinning of the lubricant. Also, if a red automatic transmission fluid (ATF) was mixed with an engine oil, there might be some type of color change.