Olav-

Having recently chased down some major leaks on my '87 535 I can suggest = the following as common problem areas:

• - Oil sender unit
• - Valve cover gasket and check cover for flatness
• - Oil pan gasket cracks and weeps on older/high milage vehicle. = Replacement requires lifting engine of it's mount to drop the pan = enough to r&r gasket. Using a good gasket sealant that tolerate = petroleum based liquids is advisable. If you do this gasket = replacement it also becomes a good opportunity to change drive belts = (alt., ps, ac) as you have to slack off on these for the pan removal. = Approx 4 hours labor
• - Rear of cyylinder head there a rear plate gasket ( I believe it's = referred to as the distributor plate gasket). Approx. 2 hours = labor.=20

Hope this helps,

Jonathan