I have a 912ULS in an RV 12. The engine has 1100 flight hours and about 1220 engine hours. About 10 hours ago I noticed a significant increase in in oil consumption, from near zero to 200 to 300 ml in 2 to 3 hours. The engine has been run on 91 AKI MO gas 95% of its life with 5% 100LL. I have used Shell Sport Plus 4 oil and changed the oil every 50 hours.
I started my research on the cause of this problem by doing a leak down compression test. All cylinders were found to be 86/87. I noticed some oiliness on the #1 spark plug so I decided to borescope the cylinders. I found all cylinders to be dry with normal deposits except #1 which was oily and had a small pool of oil at the bottom. (SEE photo) Based on previous discussions I suspect this to have been caused by a broken or damaged oil control ring.
Should I plan on replacing the #1 piston and rings?
Should I replace the #1-cylinder intake valve oil seal?
Can I replace the #1 piston by only removing the #1 cylinder head and cylinder barrel while the engine is still installed in the aircraft?
Any thoughts about the condition of the other oil control rings. Should I replace all the pistons and rings?
Mike
