Action Racing, Brad Jones Racing, Evans Motorsport, Image Racing, Minda Motorsport, MW Motorsport, Sonic Motor Racing Services and Tony D'Alberto Racing are all sharing the rural Victorian venue for the test.
Many drivers have not been on track since the conclusion of the opening round in Adelaide on March 2, where MW Motorsport's Chaz Mostert took the round win.
The 21-year-old has since left the series to join Dick Johnson Racing's V8 Supercars Championship effort.
Steve Owen has been tipped as the man most likely to replace Mostert, but is not at Winton today due to an existing commitment.
Kiwi Ant Pedersen, who is also in contention for the seat, is currently at the controls.
The Fords of Dale Wood, Kristian Lindbom, George Miedecke, Aaren Russell and Taz Douglas filled third through seventh in the standings after Adelaide, with Daniel Gaunt (Holden), Drew Russell (Ford) and Cameron Waters (Holden) completing the top 10.
Waters' Minda Motorsport team-mate Sam Walter is sporting a new livery on his ex-Garry Rogers Motorsport Holden today, reflecting an expanded presence of existing backer Blackchrome sportswear and workwear.
Today's testing follows a four-car Dunlop Series hit-out at Queensland Raceway last Thursday for the Finance Ezi Racing, Sargent Security Racing and Interquip Racing entries – all of which are prepared out of Paul Morris Motorsport's Queensland headquarters.
The Matt Stone Racing Fords and Casey Stoner's Red Bull-Pirtek Holden have also enjoyed running at the Ipswich venue since Adelaide.