xW-40 vs xW-30 for Mercedes V6 M272?

[gogydm]

Why would you switch to a low-SAPS oil in a non-direct injected engine? W30 vs W40 is irrelevant if it meets the 229.5 spec. Stick to that and you'll be fine. My car burns oil the most with M1 0W-40 so I do not use it anymore and run HPL 5W-40 Euro/SuperCar. Currently at 258k miles.

 

[altaylar]

It is exactly that, opinion.
However, don't get worked up the way people responded. You also stated how MB 229.5 is a minimum specification, and not a maximum, without actually understanding any of that.

As for what people use, well, what does make it right if they use it? Rotella gained popularity some 15-20yrs ago in Subaru and VW forums here in US bcs. there were not thick 5W40 oils and those engines were big fuel diluters. Bcs. Rotella had a higher KV100; it ended up in the high 30's at the end of OCI. People discounted other advantages of oils that carry factory approvals. Ferrari does not have an approval. Ferrari usually used whatever oil brand they have a marketing deal with (Shell). In 90's Ferrari, Shell Helix 5W40 is oil I would personally use.

I really don`t want to prolong that conversation, or give out too much personal information, but I have overseen production of certain engines in the past when I was still working as an engineer, and I am quite familier with how manufacturers grant certifications and approvals. They are based on meeting the min requirements, that your product (in this case, and oil) either puts a check mark to each box on the grid or not. If you check all the boxes, you get the approval. Just to make a hyptotehtical example, lets say that a manufacturers say "max 0.5 point viscosity lost over X hours of running the engine" and if the oil looses less than 0.5, it passes. At that point it does not matter if it lost 0.49, or 0.01, they both will get the certification if this was the only single parameter they require. So us knowing that the oil has that spesific approval would not have information on how below the threshold it performed. In the industry we called it "MinMax optimization." That, we want to Minimize the Maximum value of something, in this case, viscosity loss. And often these tests were run under much higher temperature or stress than the real engine would operate under, to be able to shorten the test duration and the cost.

This being said, I never worked for MB or an oil testing body, so I do not know what spesific performance metrics MB 229.5 evaluates, but I do not know too many tests that does not work with MaxMin or MinMax approach, which are essentially identical. And the same approach goes for the engine surface smoothness tests to oiling system design for pressure and reach, to cooling.

So overall, my understandig of a cerfitication/approval is that:
If a product carries it, it MEETS OR EXCEEDS the manufacturer requirement.
If it does not carry it, it was likely never tested for those requirements by the certifying body. If it was to be tested, it could have passed or failed, we simply do not know. (Most of the time tests are so expensive that if you are testing for it, you aim to pass. If you don`t you iterate to pass, because you made the product to carry that certification. There are rare cases where a product just fails a test, and goes its own way)

 

[edyvw]

I really don`t want to prolong that conversation, or give out too much personal information, but I have overseen production of certain engines in the past when I was still working as an engineer, and I am quite familier with how manufacturers grant certifications and approvals. They are based on meeting the min requirements, that your product (in this case, and oil) either puts a check mark to each box on the grid or not. If you check all the boxes, you get the approval. Just to make a hyptotehtical example, lets say that a manufacturers say "max 0.5 point viscosity lost over X hours of running the engine" and if the oil looses less than 0.5, it passes. At that point it does not matter if it lost 0.49, or 0.01, they both will get the certification if this was the only single parameter they require. So us knowing that the oil has that spesific approval would not have information on how below the threshold it performed. In the industry we called it "MinMax optimization." That, we want to Minimize the Maximum value of something, in this case, viscosity loss. And often these tests were run under much higher temperature or stress than the real engine would operate under, to be able to shorten the test duration and the cost.

This being said, I never worked for MB or an oil testing body, so I do not know what spesific performance metrics MB 229.5 evaluates, but I do not know too many tests that does not work with MaxMin or MinMax approach, which are essentially identical. And the same approach goes for the engine surface smoothness tests to oiling system design for pressure and reach, to cooling.

I wouldn’t know anything about it.

 

[wlk]

I would skip Castrol Edge 5W30 or 5W40 though.

Are you talking about SN vs SP versions or the whole line in general?

Just curious as I use 5w40 in none Euro vehicle so it doesn't matter all that much. It is beyond the GM/Ford 5w30 of 10w30 spec'd 90s and early 2000 required so good there. Found them on sales so happy either way.