[turbohead7]

Most 944's drop to around 1.5-2.5bar when warm. The oil pressure relief valve limits high oil pressure above 5 bar, it shouldn't affect your lower readings much. Oil viscosity shouldn't affect the guage reading much either as I've eperimented with different weights on different cars. If this is a new thing, You may have a small restriction somewhere in an oil passage, this will create an unusually high reading. 4.5 bar at idle when warm is unusual. Fully synthetic oil such as Mobil One does wonders for cleaning engines. But before going nuts thinking about the engine, oil pressure testers can be bought for about $50; finding out whether the reading is accurate is crucial to a proper diagnosis. Your problem could also be with the wiring. Lastly, I've heard of aftermarket filters causing strange oil pressure readings, have not seen this myself yet. Many people, and filter manufacturers, don't know that Porsche 944 filters have a specially designed pressure relief valve and spring. Factory filters are best, Mahle is a close second.