Engine serviced yesterday. The oilfilter is of a washable type. I opened it and since it looked like new I decided not to wash it. Changed oil, new is 15W-40 mineral oli which should be ok for this kind of a engine.
Engine started very well, and ran like a clock. Only the temperature rose rapidly, and it seems that it was only the waterpump belt which was very loose. After tightening the temperature seem to settle.