This is contig.exe it is a file that will defrag your GTA IV and gain for you 5-10 fps
Download that contig.exe file and place it in your GTA IV directory.
Then create a shortcut desktop and open the shortcut properties and put in the ''Target'' at the end -S so it would look like this
''LOCATION OF GTA IV FOLDER''\Grand Theft Auto IV\Contig.exe" -S
Then press Apply and double click the shortcut that you made now.
Then run it and wait till it close's because that means it's finished it can take anywhere from 5 to 20minutes to complete depending on your system.
Second is to turn down your view distance
(This use Magic.bat file,search it in google)
This tweak you have to open GrandTheftAutoIV\pc\data folder timecyc.dat (use notebad++)
Open it and try to find in each weather chart 1500 (which is the current distance)
It may also have a word over it as ''FarClip''
If you change it to smaller value like 500 you will see less and you will get bigger improvement
I gained 5 fps by setting it to 750 all of them
Third and the BEST !!!
Patch your GTA IV either to 220.127.116.11,18.104.22.168 or 22.214.171.124
The 126.96.36.199 works the BEST for me and i gained about 10 fps
It will work
Because the patches have the same files except the shaders are changed...
But the Contig.exe will have NO problem with 188.8.131.52
And the FarClip changing will work too...
Patch 184.108.40.206 has a lot better shadow system, BUT it takes away pretty much FPS and so does 220.127.116.11