Home » Duramax LLY » Duramax LLY – ENGINE DIAGNOSIS – Excessive Oil Consumption

Duramax LLY – ENGINE DIAGNOSIS – Excessive Oil Consumption


1. Prolonged high speed, high load, or overload operation.

2. Incorrect oil grade used for high ambient temperature operation.

3. Oil leaks at:
– Rocker covers
– Oil pan
– Rear main seal
– Oil filter
– Timing chain cover or seal
– Cooler hoses/lines

4. CDR valve or hose faulty.

5. Engine problem:
– Worn broken piston rings
– Worn valve seats or guides


1. Reduce overload, or speed as needed.

2. Switch to SG, SH-CD oil with SAE viscosity rating of 15W-40, 20W-50, or 30W.

3. Locate and correct leaks as needed.

4. Check valve and hose and replace if necessary.

5.Run compression test to verify ring problem.
Overhaul cylinder heads if guides, seals, valves are worn. If wear is premature, check injectors and injection pump. Excessive fuel will wash oil off walls/guides causing ring and valve wear.


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