What are oil approvals?

Thanks to the articles on oil viscosity and the engine oil classification, you already know that there are established methods for classifying automotive oil by quality and performance characteristics.

But, it turns out that's not enough for a lot of car manufacturers! They, apparently, go and invent their own oil approvals, and then certify engine oil against these approvals for their own engines.

In short, an engine manufacturer's approval is a specific engine oil quality standard, with defined parameters that the car manufacturer considers mandatory for oil used in its engine.

The approval process is fairly complex — in order to get the right to print some manufacturer's approval on an engine oil label, the oil producer has to obtain the corresponding certificate from that car manufacturer. In turn, before issuing such a certificate, the car manufacturer runs fairly demanding tests and analyses of the engine oil. And it's the oil producer, of course, who pays for the process (and no small amount, by the way).

Information about which approvals a particular engine oil is certified for is always present on the label (see the figure), meaning that if that information isn't there, that oil isn't certified against any approvals, whatever the salesperson tells you.

Carmakers also differ in how they approach approvals. Some (for example, the VAG group — Volkswagen, Audi, Skoda, Seat — or Daimler) develop separate approvals for different types of their engines. Others (for example, Porsche or Opel) simply test an oil for compatibility with all of their engines at once, though there are exceptions here too: Opel has different approvals for petrol and diesel engines, and Porsche approves some oils with the proviso “for all engines except…”.

Sometimes next to the approval on the can there is a note saying “meets the requirements of…”, “recommended where … is required” or the like. This means that the oil producer has awarded the approval to itself, and there is no certificate from the carmaker for this brand of oil. That alone doesn't mean the oil fails to meet the requirements: the requirements of approvals are no secret, and the big oil producers have serious laboratories of their own. But at this point it's a question of how much you trust the brand, and if you have the chance to buy an oil with a genuine, certified approval, it's better to buy that one.

And one more serious misconception: “if an oil is approved for the latest Mercedes, it will surely suit my old Volkswagen”. Approvals are developed as refinements and extensions of the universal classifications' requirements for specific engines, so an approval is not a mark of quality but rather a narrow specialisation of the oil. And for an old Volkswagen in particular, a modern oil with the latest Mercedes approvals can turn out to be, quite literally, an engine killer.