I'm not sure what current thinking is, but I find the arguments that Koine (low) Greek was commonly spoken to be more convincing to me, even if it's an unpopular view. The Gospels were written in Greek, we know that. They weren't translated from Aramaic, they were actually written in Greek. If Greek was just used by the elite, then one would expect that Luke and maybe John would have been written in Greek and the other two written in Aramaic, but all four of them were written in Koine Greek. That indicates to me that all four Gospel writers were comfortable with Greek. And it makes sense that they were, because in the multi-lingual multicultural Roman Empire, you wouldn't just stick to your native language, you'd have to know Latin or Greek just to get along. Most people would be bilingual or more. (In history, monolingualism has been the exception rather than the rule, but we forget that, since native English speakers tend to be monolingual).

And I really need to go to sleep!