In case you weren't aware, Oblivion compresses certain record types. This saves file space at the cost of performance. In the case of Oblivion, this can be quite a lot of performance, as the game uses very slow compression for its files.

This is an ESP and xEdit script that decompresses all applicable records in Oblivion.esm and mod plugins to boost performance and reduce CPU strain, at the small cost of some extra file size. Essentially, this is a plugin version of Oblivion BSA Uncompressor.

Requires the Shivering Isles DLC.

INSTALLATION INSTRUCTIONS:
1. Install the Oblivion Decompressed Records Plugin from this mod page and place it at the very top of your load order, just underneath Oblivion.esm and any other ESMs in your load order. Do NOT let ANY other ESPs load before this plugin, not even the Official DLC.

Load order example:
Oblivion.esm
*any other mods with .esm extension*
Oblivion Decompressed Records.esp
Official Oblivion DLC
Everything else

2. Download the Oblivion Decompress Records xEdit Script from this page and extract it to your TES4Edit Edit Scripts folder.
3. Boot up the 64 bit version of xEdit found in the Optional folder of your TES4Edit install, then load all your plugins. (xEdit might crash if you don't use the 64 bit version for this.)

People seem to be having issues using the 64 bit version of xEdit. You can try using the regular version but it might crash. I personally just rename the 64 bit executable to TES4Edit.exe and replace the standard one, this should fix any issues with scripts not being found. Backup your original TES4Edit.exe if you choose to do this.

4. After loading up all modules, select every plugin in your load order below this mod. Do not select this mod, any mods with an .esm extension, or Oblivion.esm/exe. (You also need to make sure you have no ESM flagged ESPs selected, but the only way to identify those is by looking at their header in xEdit or by their color in Wrye Bash.)
5. Right click "Apply Script" and select "Decompress Records (Oblivion)".
6. Run it. When it's done, make sure that "Backup Plugins" is checked when saving. This way, if something goes wrong, you can restore your old compressed mod files.

Now all of your plugins will be decompressed. Performance impact should be immediately noticeable, let me know how it goes for you guys.

Thank you to JohnathanOstrus for allowing me to use his modified script and host it here.

Absolutely not compatible with OHA. That mod is dangerous and no one should be using it anyway, but it will break things if you try to use it with this mod. If you use it, restore the default Oblivion.esm before installing this mod.

Don't clean this mod with xEdit. It has already been cleaned manually and contains no dirty edits, but xEdit will remove needed records from this mod if you try to clean it.

This mod cannot be merged into the Bashed Patch, despite technically being mergeable. The appropriate tags are included in the plugin to prevent it from being merged anyway, don't remove them.

Also check out Skyrim Decompressed Records; the same mod but for Skyrim.