Just done a complete oil and oil filter change. On the manual it says 3.2Ltrs oil and with filter 3.5Ltrs. It only took 1.75 Ltrs. Started it up to circulate oil and it all disappeared. Switched it off and it all reappeared and filled the sight glass completely. Does anyone know whether more oil should be put in whilst its running or whether I have a problem on my hands here ?