Last time I started the engine (after 3 days of parking) it did not sound good, seemed to run on one cylinder only, after a while it seemed to be ok. Today (after 3 days again- walking city-tourist : ) ) the sound seems to be worse, it sounds as if the valves did not get any oil. In addition the oil lamp is flickering, even in gear. I cannot see any obvious failure, oil level is good, screws to the exhaust were pretty tight. Later I started the engine again to show a mechanic. This time the oil lamp first did not work at all, then just in neutral, then it went off again. The last oil change is 2000 km ago. I did not have a new oil filter though (means the filter is 8000km old). There were no signs of malfunction until some days ago, The valves have been adjusted 8000 km ago. Any ideas? Thanks a lot!