Quite correct, but there are some more things to consider. In Pakistan we have no API starburst symbol on oil bottles. Starburst symbol means the company has paid to API for the certification. Using this certification fees, API regularly buys bottles of that make and model and checks whether the company is confirming to the standard or not. On our oils, just API SG etc. is printed. This means they are not certified by API, but they make their oil so that if somebody tested it for those parameters which in that API spec the oil will meet those specs. Now since all consumers don't have an independent lab and almost none has a copy of all API specs companies can go ahead and fill whatever in the bottle. Who will check?
Another point is: Not only API specs count. There are other specs also. E.g. in Europe they use ACEA standards. You can find ACEA spec ratings on Castrol bottles. [Making specs is a difficult and costly job and Pakistan being a poor country doesn't have the resources to make our own. So companies in these coutries (and some authorities too) adopt specifications from other countries and use them. Not all countries like to adopt specifications. This is sometimes due to national pride and also because some countries have problems specific to them so others' specs can't hold true for them. Fortunately USA has a big area and all sorts of extremities (temperature, humidity, dust, altitude etc.) are there so countries adopting their specs (of whatever field) aren't at disadvantage. Look at Pakistan: we have no specific problem that doesn't occur in the USA which we'd have to account for ourselves.]
Another point: Some oils not only meet but exceed the specification. The specification is a minimum standard. Example: Shell helix red bottle and Castrol GTX both are API SG but GTX is one thousand times better. This means two products can meet the same standard but still be different. I just remembered this page, which shows the fact that API have recently put an upper limit on some additives (which are good for engine but bad for environment), and the oils though excellent do not meet API specs! Their performance exceeds any standard-compliant oil. However, AMSoil (not available in Pakistan) are producers of the best oils.
One more thing: Some products are very good but the companies don't care tuppence for specs (probably because they far exceed the specs), so they don't check whether their products meet XYZ specs or not. I can't remember any oil industry example though. Just remembered, licensing is expensive and not all companies (or their customers) want to bear the additional expense.
Similarly, Havoline and Shell yellow both may be API SL, but Havoline is much better performing and its extra cost can be justified. This is because not all desirable parameters are covered by specs and manufacturers enhance those parameters sometimes which increase the cost.
