Filter diagnostics and prognostics

1. A method for a lubricant filter, comprising:

indicating a condition of the filter based on a difference between a measured pressure differential output from a differential pressure sensor and an expected pressure differential during select conditions in which all lubricant pumped by a pump upstream of the filter flows into the filter, wherein a degraded condition of the filter corresponding to a fault of a filter bypass valve setpoint is indicated if the measured pressure differential is greater than the expected pressure differential and is substantially greater than the filter bypass valve setpoint.

2. The method of claim 1 , wherein the condition is one of a nominal condition and the degraded condition.

3. The method of claim 1 , wherein the expected pressure differential is determined as a product of a lubricant flow rate and a lubricant viscosity.

4. The method of claim 3 , wherein the lubricant flow rate is determined based on one or both of a speed and a displacement of the pump.

5. The method of claim 3 , wherein the lubricant viscosity is determined based on lubricant temperature.

6. The method of claim 1 , further comprising filtering lubricant in a lubrication circuit via the pump, a filter bypass valve, and a pressure relief valve, and

wherein during the select conditions, an outlet pressure of the pump is limited to less than one or both of respective setpoints of the filter bypass valve and the pressure relief valve.

7. The method of claim 6 , wherein the outlet pressure of the pump is limited by adjusting a displacement of the pump.

8. The method of claim 1 , wherein, during the select conditions, engine speed is less than a threshold engine speed.

9. The method of claim 1 , wherein the degraded condition of the filter corresponding to partial clogging of the filter is indicated via one or more of a diagnostic code and a dashboard indicator if the measured pressure differential is greater than the expected pressure differential but is neither near nor substantially greater than the filter bypass valve setpoint.

10. The method of claim 1 , wherein the degraded condition of the filter corresponding to full clogging of the filter is indicated via one or more of a diagnostic code and a dashboard indicator if the measured pressure differential is greater than the expected pressure differential and is near the filter bypass valve setpoint.

11. The method of claim 1 , wherein a nominal condition of the filter is indicated via one or more of a diagnostic code and a dashboard indicator if the measured pressure differential is not greater than the expected pressure differential.

12. The method of claim 1 , further comprising displaying a remaining operational life of the filter based on one of the difference between the measured pressure differential and the expected pressure differential, and a frequency of filter bypass valve opening.

13. The method of claim 12 , wherein displaying the remaining operational life of the filter as a distance that, when traveled by a vehicle, prompts recommendation of filter replacement includes estimating a relatively shorter remaining operational life for a relatively higher frequency of filter bypass valve opening, and

wherein displaying the remaining operational life of the filter includes estimating a relatively longer remaining operational life of the filter for a relatively lesser frequency of filter bypass valve opening.

14. A method for a lubricant filter, comprising:

indicating a condition of the filter based on a difference between a measured pressure differential sensed by a differential pressure sensor and an expected pressure differential during select conditions in which all lubricant pumped by a pump upstream of the filter flows into the filter,

displaying a remaining operational life of the filter based on one of the difference between the measured pressure differential and the expected pressure differential, and a frequency of filter bypass valve opening,

wherein displaying the remaining operational life of the filter includes estimating a relatively shorter remaining operational life for a relatively higher frequency of filter bypass valve opening, and

wherein displaying the remaining operational life of the filter includes estimating a relatively longer remaining operational life of the filter for a relatively lesser frequency of filter bypass valve opening.