Cameron Dawson powered to victory by more than three seconds at Oulton Park, as Owen Jenner closed in on points leader Aaron Silvester.
After a faultless start, Dawson led into turn one and already had more than a second in hand at the end of the first lap, a lead he extended over the rest of the race to eventually beat Jenner by 3.261secs.
Following a charge from the second row, Jenner spent most of the race battling with Sam Laffins, who eventually finished third.
Asher Durham was fourth with Harrison Crosby fifth as Silvester took seventh, letting Jenner close the gap to just seven points with three races to go.
Pirelli National Junior Superstock with Santander Consumer Finance, Race result:
1. Cameron Dawson (MSS Performance)
2. Owen Jenner (Jenner Racing) +3.261s
3. Sam Laffins (G&S Racing) +3.344s
4. Asher Durham (G&S Racing) +4.871s
5. Harrison Crosby (JR Performance Racing) +5.949s
Championship positions after Round 12:
1. Aaron Silvester 213
2. Owen Jenner 206
3. Asher Durham 191
4. Cameron Dawson 183
5. Jacob Hatch 127