Donald took over the early lead from McGuinness on Lap 1 of the four-lap race. By the time riders came in for the only pit stop of the contest after Lap 2, Donald's lead was unassailable and the Suzuki pilot motored on to a 15-second the victory.
McGuinness, who holds the standing TT lap record at 130.345 mph, tried to catch Donald but 0.438 mph separated the two at the finish. As for Martin, the Englishman managed to edge out the impressive Kawasaki rider, Ryan Farquhar, and whittled his way up to within five seconds of his Honda rival.
Finishing behind the ZX-10R-equipped Farquar was Yamaha's Conor Cummins. Saturday's third-place finisher, Suzuki's Adrian Archibald, scored a sixth-place finish on the Superstock machinery, with YZF-R1 riders Ian Lougher and Steve Plater taking the seventh and eighth spots. Suzuki's Carl Rennie ended the day ninth and Yamaha's Daniel Stewart rounded out the top 10.
As for Saturday's second-place Superbike finisher, Bruce Anstey, the TAS Suzuki rider pulled into the pits at the halfway mark.
2008 Isle of Man Superstock TT Results:
1. Cameron Donald (Suzuki) 125.776
2. John McGuinness (Honda) 125.338
3. Guy Martin (Honda) 125.253
4. Ryan Farquhar (Kawasaki) 124.756
5. Conor Cummins (Yamaha) 124.605
6. Adrian Archibald (Suzuki) 123.596
7. Ian Lougher (Yamaha) 123.103
8. Steve Plater (Yamaha) 122.897
9. Carl Rennie (Suzuki) 122.732
10. Daniel Stewart (Yamaha) 122.285