A perfectly elastic collision would still be the same - the energy is still conserved and divided equally between the two cars.
Assuming the cars are of equal mass. If not, the heavier one will drive the other car backwards faster, and the energy will not be divided equally between them. But the sum will remain the same.
Assuming the cars are of equal mass. If not, the heavier one will drive the other car backwards faster, and the energy will not be divided equally between them. But the sum will remain the same.