Here’s a practical, step-by-step guide to fixing lag/stutter in (Steam/Rockstar Launcher). This game is notoriously poorly optimized, but these fixes work for most users. 1. Apply the essential commandline.txt tweak Create a commandline.txt file in your GTA 4 install folder (where GTAIV.exe is).
C:\Program Files (x86)\Steam\steamapps\common\Grand Theft Auto IV\GTAIV gta 4 complete edition lag fix