If my Oil filter is completely sludged up, will my Oil pressure always show in the Bypass range?

It gets to 40Psi Hot at Idle, and goes Straight to 65-75 Psi, even Hot, all other times.



I do not know how to change just my Filter.



Is it Bypassed and Sludged, the Filter? Should i change the oil at the same time as well?



I fear that the filter i bought may not be the same size it listed twp different numbers and it looks different than what came out of my car, and then id be in trouble due to losing oil and no Filter.



Car is 1985 Jaguar 4.2L, filter i picked up is a Bosch 72209.



Where is the filter on my Jag, and how do i change just it? How much oil will i need to replace if Just the Filter?If my Oil filter is completely sludged up, will my Oil pressure always show in the Bypass range?It can do that. And im Sorry, i dont know where your Oil Filter is.