Yes, the onus (and cost) is on the blender to get a certification from any car manufacturers.
However, to be able to sell in certain markets, such as US, Europe, they have to follow certain industry standards as a minimum, which are set and tested by national/federal govt agencies, eg ACEA etc
As a result, the oils will have some national certifications and some manufacturer certifications. Ofcourse, this is only relevant in oil lubricants.
In addition, the blenders make 100s of other products, eg performance additives, sealant lubes, anti-leak additives, glues, anti-freeze coolants, windscreen washer mixes, etc.
None of these undergo any testing by auto manufacturers. Their quality can vary from product to product, or manufacturer to manufacturer.
Having said that, it is fairly easy to notice the world over that LM products are known for their quality.
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