When I was in the industry I never saw or heard of an example of a bulk oil distributor willfully substituting a cheaper/lesser branded product and passing it off as a more expensive product, though I'm sure it happens.

To the point of prepackaged lubricants being easily traceable, honestly that's not as cut and dried as one might think either.

It was common knowledge and an ongoing joke in the industry that one brand in particular changed who blended and packaged it every time the individual containers or case configuration changed, which often took place at least twice annually.

Working for a Shell distributor I learned from the drivers who delivered our bulk Shell oil that Shell facilities were themselves the cleanest and most demanding of all the oil bulk load out facilities. Shell utilized electronic sniffers that they would drop down into bulk tankers before loading and if a trailer was considered contaminated they had to get out of line and go have their tank washed out, then reinspected before they'd be allowed to load.

As we also were open to the public and sold all the major brands of oils used by truckers, along with complete air/fuel and oil filters for over the road trucks, we had a lot of owner/operators as customers.

One such customer hauled mostly drilling pipe to remote drilling facilities and claimed again Shell was the pickiest of all such customers, requiring that each stack of pipe had to have wood layers between the pipe, the whole trailer had to be tarped and lastly that they would inspect the ID bores of the pipe to insure cleanliness before allowing him to unload it at a Shell drilling rig.

BTW, Shell oil in the US is no part of Shell in the rest of the world. They bought themselves away from the international Shell consortium many years ago and operate completely independently from them.

One last interesting fact about Shell in WWII. Prior to the war Hitler was seeking a lubricant/fuels supplier for his reich machine and Shell was headed by a Hitler sympathizer who told the board at Shell he intended to BE that supplier. The board was in shock and did not want such a deal, but fate stepped in and within a week or so of the deal being penned by Hitler and Shell, the CEO died and Shell withdrew the offer