Originally Posted By: ZeeOSix
Originally Posted By: goodtimes
The way I read the GM statement, the oil sender WAS placed before the oil filter, on the oil pump output, and now they put it after in the galleries on those particular engines. This could explain pressure and noise problems when using different filters on these engines with feedback relief valves. I thought it was excellent information from GM.
How I read it is the pump's pressure relief valve is controlled by the pressure sensed in the main oil gallery instead of at the pump's output port. So if there was a reatively flow restrictive filter installed, the pump would work harder without hitting pressure relief to maintain required oil pressure in the main oil supply gallery. It's to ensure the engine isn't starved of oil, so shouldn't be causing any engine noises or oil pressure problems if working correctly.
That method of oil pressure control has no association with where the sensor for the oil pressure gage on the dash is located.
The oil filter bypass valve setting isn't dependant on the oil pressure, just the delta-p created by the media's flow restriction, the oil temp/viscosity, max holding capacity and the max expected oil pump flow volume.
However, when the variable relief valve opens or closes the dash pressure will change from the changed flow. It may explain the unexplainable pressure reading changes between filters reported here. In these cases I would only use the GM recommended filter. The details they added in the statement explains a lot why sometimes one size does not fit all.
