The engine for Postal 2 is kinda weird. It's like a combination of Unreal Tournament and UT Most of the subsystems are. Postal 1's engine is RSPiX (as stated above), Postal 2's is a modified Unreal 2 (also stated above), Postal III's is Source (one of the pre-HL2: Episode Two builds. POSTAL 2. All Discussions Screenshots POSTAL 2 > General Discussions > Topic Details This game seems perfect for the Source Engine.