A few years ago I installed new custom made 'Airequip' hoses to and from my oil filter canister on my 235. I noticed over time there was a drop in oil pressure at all engine speeds. I blamed my original gauge for reading wrong and installed an aftermarket unit. My original gauge seemingly read correctly.
At speeds of 35-40 MPH I was reading about 25-30 PSI. Idling at traffic lights it went down to 10 PSI.
Today I removed the oil filter assembly and plugged the holes in the block. A test drive at normal operating temps gave me a 40-45 PSI reading at speed and nothing less than 25 PSI at idle.
I know by-pass oil filters can rob your oil pressure a bit but not this much. The only thing I can think is that the inner diameter of the 'Airequip' hoses was too large. It was probably a good 1/8".
Anyway as I change oil every 1000-1500 miles I think I'll leave the filter off the truck.
