Cheat Codes:

The cheat used in KKnD (original) for 32 mil in oil credits can be used in KKnD Xtreme as well, here it is again: 

KKND & KKND Xtreme Save Game Oil Cheat

A cheat to get heaps of oil credit in KKND or KKND Xtreme

Begin a level and then save the game. Use a hex editor - I use XTGOLD - In XTGOLD highlight the saved file and then press V for view, H for Hex, E for edit. After you have edited the hex press enter, Esc and quit XTGOLD. Now go back to KKND/KKND Xtreme and restart your saved game. In the Survivors levels the first line of your hex will look something like this:

000000 0100 0000 0000 0000 0000 0000 0000 0000

Regardless of the numbers that may be in your saved game change this to:

000000 0100 0000 0000 0000 F301 F301 F301 0000

This will give you over 32 million oil credits.

In the Mutants levels your hex will look something like this:

000000 0200 0000 0000 0000 0000 0000 0000 0000 

Change this to: 000000 0200 0000 0000 0000 0000 FFFF FFFF FFFF

This will give you a negative oil figure with the result that you will never run out of oil credits.