INSTALLATION AR-HYDRAULIC HAMMER 7Y5712 - Caterpillar

of these truck engines may notice that the used engine oil is darker in color than other 3406C engines. The darker color is caused by additional soot in the oil. The additional soot is a result of the 1995 combustion system. Testing has show that the additional soot is not detrimental to the operation or life of the engine.
Caterpillar recommends following the published oil change guidelines in Operation And Maintenance Manual, SEBU6746-02, 3306C/3406C ATAAC Diesel Truck Engines, 9TL1-Up, 8PN1-Up, 5KJ7800-Up, 3ZJ16182-Up.
If the color of the used oil continues to be a cause for concern, Caterpillar suggests enrolling in Scheduled Oil Sampling (SOS) at your local Caterpillar Dealer to monitor engine and engine oil condition.