The Scot is through to the quarter-finals of the California-based tournament after beating his Chinese opponent 6-3 6-2 in a match that lasted just one hour and 28 minutes.
The world No. 3 was never unduly troubled by the World No. 79 and stormed ahead in the first after a back-and-forth rhythm to the set saw the pair take three games each.
Lu offered little resistance to Murray in the second and Murray dominated the set to advance.