There are only a few lubricant blenders, who package accordingly. At the moment we use Vauxhall Trade Club oils. I have a reasonable idea who blends their products, but I'm not 100% sure. They meet all the required spec.

My personal view is that a lot of horse-trading goes on between blenders and car makers, mostly to the detriment of the smaller independent garages and the consumer.

We have just stopped buying 10w40 in barrels. We keep a couple of different 10w30s in barrels and the rest in 25s to satisfy the various makes.

My family ran a 'Shell' branded petrol station for most of the 20th century, 1930s-1990s. We have photos in the archives of 'BP' tankers dropping fuel into the tanks at busy times. Despite this there were consumers that swore that their car ran better on Shell/BP fuel (delete as appropriate).