New GM ad campaign: "dexos1 Gen2: Not Just for Breakfast Anymore"
dexos1 tests are run after all the usual SN, GF-5 tests have been run, so you can already see its a 'generic' spec.
Then, dexos1-unique tests pull some ACEA tests in (European), so you can see its also a Euro spec to some degree, using Euro engines for tests.
After that, other tests are run which further validate the oil for more types of seals, LSPI in GM engines, chain wear, oxidation tests, .... but its all applicable to any non-GM engine.
For all American, Japanese, British, & Korean makes anyway. Germans do their own thing, although the full-syn versions of dexos1 Gen2 would probably work fine in BMW's too since BMW went HTHS<3.0 recently in almost all their engines. BMW, VW, and Mercedes have their own specs, and should be followed though.