[bluedog]

that is a known issue, due to very narrow oil drain holes inside the piston ring grooves.

When the oil becomes hot enough (right at the piston is approximately the hottest spot within the engine, which is reached by the engine oil), it tends to plug up those tiny but important drain holes.

Another possible cause for oil consumption are the valve seat rings. That would cause oil smoke after an idle-phase, when you turn up the engine. It's quite more probable, that its the first, above mentioned cause.