Growing up the the 80s I'd heard Davison through Highland Park referred to as 4 Mile.

The way McNichols turns NE at Gunston, I'd say it's no longer 6 Mile, and Seymour is closer to being 6 1/2 Mile, but Spring Garden is closer to the true 6 1/2 Mile.

Houston Whittier is the true 6 Mile on the east side, and it even continues the same directional pattern as Moross and Vernier, although its name changes to Whittier.

But even though they are each a mile apart, Whittier, Moross and Vernier, while extensions of Mile Roads, really are not. As has been pointed out, 7 Mile and 8 Mile both continue on east past where Moross and Vernier start.

And I have no idea how 3 Mile Drive got its name.