Mercedes approved oil?

A good reason to charge you more for oil.    Look in your owners manual.  It probably gives you a MB approval number,  something like 229.3 or 229.5 or something similar.   Then it gives you the oil viscosity rating such as 5W30 or 10W40.     Mobil 1 European Car Formula 0W 40 will work.    It is more important to change the oil and filter more often than what they recommend,  specially if you live in an area with a lot of dust.    I changed my every 5000 miles.   

Read the label. It will tell you what specs it meets. Most reputable companies top spec oil will meet all but the most extreme cars requirements. Even Halfords own brand synthetic oil meets Porsche specs, I don’t know about Mercedes but I would it’s very similar. If in doubt Mobil 1 will be ok.

The viscosity rating is the most important thing.

If that thing will not run on Mobil one Turbo oil I would sell it. Mercedes the company that used a 2 Cent O-ring on some of their oiling systems that led to catastrophic engine failure. Interesting fact that Hardly a Davidson tells customers the same thing but they run Mobil one in their race bikes. So apparently puttering around town is tougher on an engine than drag racing.

It's your vehicle, so it's up to you - but as long as you've been using the correct weight oil, and one that is formulated for turbocharged vehicles (Mobil 1 European Car Formula Full Synthetic for example) then you shouldn't run into any problems.

The only issue you might run into is if you have to make a warranty claim - so make sure to keep receipts and a logbook.  You can find manufacturer recommended maintenance schedules online for any vehicle.

Nonsense!

As long as what you’re using fully meets or exceeds the oil specified by Mercedes then you’re fine.

That’s exactly what Mercedes do when they buy oil and then resell it in their own branded packaging with a big mark-up on whatever they paid for it.

The only bit he’s right about is that you don’t deviate from those oil specifications when there’s a turbocharger involved.

Check the specifications on the packaging of the oil you use, but as long as the oil grade is correct, then you’ll find pretty much every brand name and even budget brand fully synthetic oil is highly likely to meet Mercedes own minimum standards. Just don’t take that for granted though and always check the packaging: even on oil brands you regularly use as they can and do change specifications without any announcements.

so you want info after you blew the warranty instructions ?.......

READ THE MAINTENANCE SECTION IN THE OWNERS MANUAL FOR YOUR VEHICLE.

Look up the spec for the Mercedes-Benz oil that is required and see what the exact wording is.  Does it say the oil has properties that exceed the standards and is required for the engines. Or does it say that the oil meets the standards and is recommended for the engines.  If it meets the standards, any oil meeting those standards is equivalent. This should be stated in the Owner's manual.