• Step 1) Open Steam Games List
  
• Step 2) Right Click GTA IV and select 'Properties'
  
• Step 3) Select 'Launch Options'

Go to C:\Program Files\Steam\SteamApps\common\grand theft auto iv\GTAIV and create a shortcut on the LaunchGTAIV.exe (right click, select “Create Shortcut”)

You can add any launch options to this new shortcut.

To launch the game properly, first start the RGSCLauncher.exe in
C:\Program Files\Steam\steamapps\common\grand theft auto iv\RGSC .
Then launch your newly created shortcut.

You will not have access to the Steam overlay while launching this Shortcut. However, once you have added these launch options successfully, you can re-launch your game from the Steam application to continue using any new changes.

Tools:
-benchmark: Runs the benchmark tool and immediately exits game.
-help: Display list of all command line options

Graphics:
-renderquality: Set the render quality of the game. (0-4)
-shadowdensity: Set the shadow density of the game. (0-16)
-texturequality: Set the texture quality of the game. (0-2)
-viewdistance: Set the view distance of the game (0-99)
-detailquality: Set the detail quality of the game. (0-99)
-novblank: Disable wait for vblank (No Vsync)
-norestrictions: Do not limit graphics settings
-width: Set width of main render window (default is 800)
-height: Set height of main render window (default is 600)
-safemode: Run the graphics in the lowest setting possible
-frameLimit: Limit frame to interval of refresh rate
(ex If refreshrate is 60HZ –frameLimit 1 = Locks down to 60HZ)
-refreshrate: Set the refresh rate of main render window
– Warning - Monitor must support (ex. –refreshrate 60)
-fullscreen: Force fullscreen mode
-windowed: Force windowed mode
-availablevidmem: Set amount of physical Video Memory(ex. –availablevidmem 0.9)
-percentvidmem: Percentage of video memory to make available to GTA
-lazydelete: Seems to hold stuff on VRAM

Audio:
-fullspecaudio: Force high-end CPU audio footprint
-minspecaudio: Force low-end CPU audio footprint

System:
-noprecache: Disable precache of resources
-nomemrestrict: Disable memory restrictions