Repair-It

So it's been roughly 3500 miles and I should change the oil since I don't know what's in there.

I should also consider fixing the rear diff fill plug that's stripped, but I appear to have fixed the earlier leak there by re-rtv'ing the plug in and cleaning the vent out that was stuck.

I think based on the Benz site Castrol Edge Euro Car passed the 229.52 spec so it should be the right stuff:
https://operatingfluids.mercedes-benz.c ... /229.52/en

However, the Walmart listing seems to only show 229.5 approval, not 229.52. Either way it seems cheap enough and probably what I'll run.
https://www.walmart.com/ip/Castrol-EDGE ... om=/search

229.5 is correct

https://operatingfluids.mercedes-benz.com/sheet/223.2

229.5 for M133 (and just about every other gas engine). .52 is generally for diesels.

You can run the same stuff as your M278. I would insist on API SP. And maybe 5W-40 instead of 0W-40 for a high performance application.

I missed the AMG note in the owners manual about 5W40 only. I'll have to return and reorder.

https://www.mbusa.com/vcm/MB/DigitalAss ... GLA%20.pdf

The only SP Castrol Euro at Walmart is 0W40.. Also Walmart apparently only has one bottle.
https://www.walmart.com/ip/Castrol-EDGE ... om=/search

Quaker State, SP, 5W40, says it's MB 299.5 approved but I couldn't find it on the MB list:
https://www.walmart.com/ip/Quaker-State ... irect=true
https://operatingfluids.mercedes-benz.c ... t/229.5/en

Apparently this is what I had been ordering for the GLS550:
https://www.amazon.com/Castrol-03101-0W ... 120&sr=8-7

I think you can run 0W-40. I just think 5W-40 is a little more robust.

Motul has some good oils as well.

For example: https://a.co/d/awaXwzS

Price isn't bad, either.

And this appears to be back: https://a.co/d/4mErYGg