Oil light on or flickers at idle? Bad sender? (usually not). Low oil pressure? (Probably). This is a typical problem with Saab 204, 205, 235 engines from a 9-3’s & 9-5’s. How to mechanically read pressures an easy way. It is a royal pain to adapt a mechanical gauge to these engines. Typically the sender is located behind the starter. Here is what I came up with and have been using for years at Mile Hi Automotive in Denver, CO. Oil filters are easy to remove and replace. Unscrew the filter and screw on the test filter, connect the hose. I have created an oil filter where I soldered an adaptor to where we can connect a mechanical gauge and read pressure accurately. I just created one for a 9-3 SS, 4 cylinders. With a long hose, you can run the hose up from the bumper and tape the gauge to the windshield and test drive. This is so simple and accurate to determine if you need a oil pressure sender or major engine repair, possible sludge. Usually low oil pressures are from sludge. I also created a scraper made from a 1/8” welding rod. Bent a 90 degree on the end raising 3/8” and created a scraper blade end. You can go in through the oil plug, insert the scraper and try to dislodge some of the sludge.