Oil supply apparatus of internal combustion engine

An oil supply apparatus, comprising an oil supply passage that allows oil stored in an oil reservoir unit to be supplied to a plurality of lubrication sections of an internal combustion engine and recovers the oil into the oil reservoir unit, a pump unit that discharges the oil stored in the oil reservoir unit to the oil supply passage,

• the pump unit being controlled to have a plurality of different stages of oil discharge pressure varied in an increase amount of oil discharge pressure of the pump unit per the rotation speed of the internal combustion engine in response to the rotation speed area of the internal combustion engine, the pump unit having a plurality of switching discharge pressures each changed for each of a plurality of target rotation speeds when the rotation speeds of the internal combustion engine reach the plurality of target rotation speeds, respectively, and
• an abnormality determination unit being operative to set in advance the target rotation speed corresponding to an arbitrary switching discharge pressure selected from among the plurality of switching discharge pressures, and to determine that the level of oil stored in the oil reservoir unit is lowered under the condition that the deviation between the target rotation speed of the internal combustion engine set to correspond to the arbitrary switching discharge pressure and the actual rotation speed of the internal combustion engine actually detected when the oil discharge pressure reaches the arbitrary switching discharge pressure is not less than a determination value.