Dunlop posted the 21st fastest time after completing 17 laps, putting him ahead of Honda Racing riders Takumi Takahashi and Ryo Mizuno, and Republic of Ireland’s Brian McCormack on the FHO Racing BMW.
Showdown contender Glenn Irwin (Honda Racing) was 11th fastest, with brother Andrew fifth on the SYNETIQ BMW.
Dunlop is the latest stand-in rider for Danny Kent, who continues to recover from injuries he sustained in a spill at Donington Park.
The Ballymoney man was in action in the previous round at Silverstone, where he rode the Dynavolt Triumph for Simon Buckmaster’s PTR-run outfit in the Supersport races as a replacement for injured American Brandon Paasch.
Dunlop is renewing his links with the Hawk Racing team to ride the GSX-R1000 alongside Gino Rea at the Cheshire circuit.
He won the Senior TT for Hawk Racing in 2017 on the Bennetts Suzuki and was also victorious around the Mountain Course on Hawk-backed BMW machinery, clinching a Superbike and Senior double on the S1000RR in 2016.