Assuming you have 8GB RAM, your CPU is a bottleneck, I would consider replacing your CPU
(Checked by Game Debate: http://www.game-debate.com/games/index.php?g_id=1308&game=Grand+Theft+Auto+V&p_make=Intel&p_deriv=Pentium+G630+2.7GHz&gc_make=Nvidia&gc_deriv=GeForce+GTX+650+Ti&ram=8&checkSubmit=#systemRequirements)