This is a CAT Fuel Filter / Water Separator
Key details:
• Brand: CAT Caterpillar
• Part No: 138-5736 - I can see it printed on the side
• Type: UHE Ultra High Efficiency fuel filter
What it’s used for:
It filters diesel fuel before it gets to the engine injectors and pump. It does 2 jobs:
1. Filters dirt/rust - Traps particles so they don’t clog injectors or damage the fuel pump
2. Separates water - Diesel often has water in it. This filter separates water and collects it at the bottom so it doesn’t go into the engine