Phil Hughes made 84 and 38 to ensure he still tops the aggregates for the tour with 436 runs.
David Warner is return into the No.6 position at Hughes' expense following his 193 for Australia A in Pretoria.
QUICK SINGLE: Starc says he has the arm for Third Test
Nathan Lyon (1-99) bowled decently but only took the one wicket.
Selectors face a tough dilemma over whether to stick with 19-year-old Ashton Agar (1-66), or elevate the more experienced Lyon.
Both finished with two wickets apiece in their supposed 'bowl-off' for the final place in the pace attack for Manchester.
At close on the final day of the three-day fixture, Australia were 2-152 in their second innings, after Sussex had earlier declared with a two-run first innings lead at 7(dec)-368.
Starc said he didn't view it as a selection trial.
"We certainly weren't taking it as a bowl-off; it was just to go out there and perform," he said.
"I tried to put the thought of pushing for selection out of the picture and just try and take wickets."
Khawaja appears set to hold onto the No.3 position for the third Test by virtue of top scoring for Australia at Lord's with a second innings 54.
But Khawaja's scores of 40 and 1 at Hove left plenty to be desired, and he's failed to completely lock up his place, with Warner waiting in the wings.
Starc said Australia had got what they wanted out of the match, with the exception of some sloppy dropped catches which prevented them from bowling Sussex out.
"It was a good game to get what we wanted in terms of time at the crease and for some of us overs under the belt in the middle as opposed to in the nets," he said.
"It was good to get some competitive time in the middle for a lot of us who haven't had too much of that I suppose.
"We probably need to be a little bit tighter and shut that scoreboard down. It definitely helps when you hold your chances."
The certainties to come out of the match were that Smith's 102no should ensure he's there for the rest of the series, wicketkeeper Matthew Wade unlikely to play as a specialist batsman after making 0 and 30no, and pace bowler James Faulkner (1-55) has a way to go yet.On day three, England squad member James Taylor showed Australia how to bat 'ugly', bringing up an unbeaten 121 that was nearly six hours in the making.