I wound up googling this super-fast (no pun intended) and found this link. You may find the Silver/Bronze Age info helpful:
Link "Super Speed: Superman's speed increased to the point where he could travel faster than light. Several stories depict him traversing great distances through space to other solar systems and distant galaxies and even other universes. He could cross our own solar system in minutes. He could also use this power to travel through time, as shown in his boyhood visits to the 30th century as a member of the Legion of Superheroes. Superman can also swim at speeds approaching Aquaman's speed as well as run at speeds similar to that of the Flash. Superman is unable to beat Flash in a race."
