Oil level in 924s is not stable

[GraemeB]

I live in Spain and Scotland. When I return to Scotland for a few weeks the Porsche oil level rises. When I return and drive in Spain the oil level starts to drop..and drop...and drop. The engine runs perfectly.
Very worrying to me and I don't drive far. There are no drops on the garage floor and no smoke from the exhaust. I suspect the oil is still in the engine and that the engine needs cleaning inside. Has anybody got experience of this? What should I do?

[Bradical]

Oil consumption on these cars are pretty high, 1-1.5L per 1000km new according to the factory. There is no where in the engine for oil to "hide" because it's dirty. Keep the oil level close to the upper mark on the dipstick and monitor your oil PRESSURE. If your oil pressure is staying around 2-2.5bar warm at idle and 4.5-5bar at cold idle you are good.

If you think you may be burning oil, have a leak down test done. How many miles on the car? General consensus on this board is that you should plan on replacing rod bearings at 150k, but most people don't bother doing piston rings (which would be the culprit behind high oil consumption) unless there is a problem with compression because the cylinders on these engines cannot be bored by conventional methods and usually stay in excellent condition well past 200k miles.

I recently blueprinted an engine out of a car that as fairly abused and was reported to have around 180k miles. The cylinder walls, runout, main and rod bearing clearances were all within spec.