first Cup race of 2018 the week after at Atlanta Motor Speedway. By the Easter off weekend, Chastain had expanded his Cup schedule, which had included every race since Atlanta, to all of the race weekends where the Monster Energy NASCAR Cup Series and NASCAR Xfinity Series run at the same track. Chastain also returned to the truck series at Iowa on an off week for the Cup Series and a companion race with the Xfinity Series, driving the No. 50 truck for Beaver Motorsports. He continued to run most of the Cup schedule, running the entirety of the summer schedule save for the Sonoma Raceway event, where Justin Marks drove. Chastain tied his career-best finish Xfinity Series finish at Iowa Speedway, avoiding last-lap chaos to bring home another fourth-place finish. At the Xfinity Series race at Mid-Ohio, Chastain and Joey Gase made contact multiple times on the final lap, eventually leading Gase to spin off track. On pit road after the race, Gase swerved his car toward Chastain with spectators and crew members in the vicinity. The two later had a shouting match and Gase was tackled by one of Chastain's crew members. After a trip to the NASCAR hauler, Gase called Chastain a "golden boy" and threatened to derail Chastain's playoff hopes. Chastain hopped in the Premium Motorsports No. 15 truck for the World of Westgate 200 and finished seventh, Premium's best-ever finish across all three NASCAR national series. On the strength of a summer performance that saw him hold down the final Xfinity Series playoff spot, Chastain and Chip Ganassi Racing announced a three-race agreement for Chastain to pilot the organization's No. 42 entry for races at Darlington Raceway, Las Vegas Motor Speedway and Richmond Raceway. The races came at the expense of John Hunter Nemechek, who could not sell sponsorship for the races. DC Solar was announced as a backer for Chastain's effort. Chastain had previously met the CEO of DC Solar at Auto Club Speedway in 2018, and plans materialized from there. For the first race of the trio, Chastain held top-ten spots in both practices, finishing second in first practice. He later claimed the pole over Christopher Bell, and during the race won the first two stages. During the third stage, Chastain was battling for the race lead with Kevin Harvick with thirty-five laps to go. Through turns one and two of the traditionally