The pair were fighting over third place in today's second Supercars race when they came to blows at the final two corners.
Mostert tried to go around the outside of Courtney at the penultimate corner but was carted wide, before hammering the back of the Tickford Ford and sending it into the wall on the outside of the final corner.
Courtney got going again and finished ninth while Mostert finished fourth on the road but was handed a post-race penalty that dropped him to 22nd.
Speaking after the incident the pair didn't see eye to eye on the incident, each believing the other will change their tune after seeing a replay.
"I'm not a lawnmower," said Mostert about being run wide. "If Courtney looks back at it, I'm not here to do the lawns around the grand prix.
"You've got to give respect to get it back. When you constantly play the old 1984 game, you've got to give some room.
"Even if the guy goes to the outside, we're side by side, you can't just run him onto the grass, or that's what results in the last corner."
Courtney added: "It's disappointing. We race pretty hard and I like to race hard and fair, but I felt that was a bit outside the boundaries.
"Last lap, we'd been pushing really hard, to have the podium taking away from us was pretty disappointing.
"I think he probably would agree when he sits down and cools down."
The pair will start sixth (Courtney) and seventh (Mostert) in today's third heat for the Melbourne 400.
