* Valve Cover Gaskets: This is the most common suspect. Even a slightly imperfect seal or improper tightening can lead to a slow weep when oil pressure is high (during engine operation). Check carefully around the valve covers for any oil residue.
* Rear Main Seal: This seal seals the crankshaft where it exits the engine block. While less likely to leak only when running (often they leak constantly), a small, slow leak could show up only when oil pressure builds up. Look for oil dripping from the rear of the engine. This is trickier to assess.
* Front Crank Seal: Similar to the rear main seal, a leaky front crank seal can cause a small leak, more pronounced when the engine is under pressure. Check the area around the crankshaft pulley.
* Oil Pan Gasket: While less likely to be a leak *only* when running, a small imperfection or incomplete seal could cause a slow leak that worsens under pressure. Inspect the bottom of the oil pan and surrounding area.
* Loose drain plug: A simple, yet often overlooked, possibility. Make sure the oil drain plug is tight.
Troubleshooting Steps:
1. Thorough Visual Inspection: Carefully examine the entire engine, paying close attention to the areas mentioned above. Use a clean rag or paper towels to wipe down suspected areas, then run the engine briefly and check again for oil leakage. Use a flashlight to get a good look into crevices.
2. Pressure Test (if possible): An oil pressure test can help identify leaks under pressure. A professional mechanic can perform this.
3. Check Oil Level Regularly: Monitor your oil level frequently to track the leak rate. A slow leak might not be noticeable immediately.
4. Professional Mechanic: If you can't pinpoint the leak, it's best to take your vehicle to a qualified mechanic. They have the experience and tools (like dye tests) to diagnose the problem effectively.
Don't ignore the leak. Even a small oil leak can lead to significant engine damage over time. Address it promptly.
