Their two-round total at the par-72 $3.5 million tournament, 10-under 134, leads Brad Bryant (68) by one-stroke with Cliff Kresge (69), Michael Bradley (69), Estanisloa Goya (67), and Bryce Molder (69) all at 8-under 136 and tied for fourth.
After Thursday's first 18 holes, Jones shot 2-under 70, but was not on the leader-board because front-runner Derek Lamely shot 6-under 66, Kevin Stadler, Molder, Bryant, Kresge and Bradley shot 5-under 67, and six others shot 4-under 68.
Friday, Jones, who started on the back nine, eagled the par-5 second, then added six birdies to record his best round this season.
In his 39th professional event, Day compiled one double-bogey and two bogeys with seven birdies, three coming at the first three holes.
Notable deaths of 2014 [PHOTOS]