The first thing to determine–via the Owner’s Manual–is whether the mfr specifies that synthetic oil must be used. If the mfr specifies synthetic oil ONLY, then you shouldn’t even be considering the use of “dino” oil.
That being said, all oil–regular or synthetic–gets dirty at the same rate, and that is why vehicle mfrs specify the same oil change interval for their engines, regardless of the type of oil that is used. Synthetic oil definitely has some advantages, but it can’t magically remain “clean” for longer than regular “dino” oil.