Meeting auto maker's oil requirements/approvals are a good thing, but they don't necessarily tell the whole story. In most cases I suspect the decision by an oil company to seek auto maker approvals are driven by money, market, or reputation as opposed to actual performance.
To be considered as factory or service fill for auto makers the approvals are probably required, i.e. winning the contract requires meeting the auto maker's specs. Approvals are costly, but can be justified with the award of a factory or service fill contract. Alternately, an oil manufacturer may seek auto maker approvals to protect their market share and/or product reputation.
However, as time passes on, auto maker specs are updated or superseded and some become obsolete. Eventually, it makes little economic sense to run tests and obtain approvals for oils that haven't been specified by auto makers for years and no longer apply to the majority of vehicles on the road. We are probably seeing an example of that now with GM 6094M and GM 4718M being replaced by Dexos. True approvals to GM6094M and GM4718M may no longer be possible for new formulations, like the ones that now meet SN/GF-5.
It should not be assumed (nor is it by most here) that any particular spec (either oil industry or auto maker) represents the “best”. Oils are formulated to strike a balance between many performance factors, and an oil maker may choose to market an oil that does not meet some of the more common specifications, but none-the-less meets many stringent requirements. In such cases, the oil may be “weak” on auto maker approvals or industry licenses, but strong on performance in many areas. For example, an oil might be formulated to maximize protection at the expense of failing the fuel economy or catalyst requirements of many auto maker's specs. This is an example of a niche market where auto warranties may not apply and volumes are low. In these applications, it may make no economic sense (because of the high testing and approval costs) for an oil manufacturer to seek auto maker approvals. It should be stressed that this can also be the case even if the oil would meet all of the auto maker's requirements. In either case an oil manufacturer may deem it appropriate to use “recommended for” or “suitable for” wording.
The obvious down side is that an oil maker may use the above wording even if the oil wouldn't come close to meeting the auto maker's specs (if it were tested). In that case the customer will never know that the “recommended for” oil he bought may not be what he intended to use. (Unless his butt dino tells him
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