I don't know that I can offer any useful comments to Dustin, however, the fact that this subject was addressed today caused me to get interested in reviewing the entire thread.

John's comments regarding the concave bottom plate in the oil tank caused me to consider that Rotax may have had added this feature without explaining their reasoning behind it. I don't think it was a conspiracy to keep us from using quick drains.

I don't know what that date was; but, if I recall, Rotax introduced "INF" (international fine thread) fittings, otherwise understood as "AN" fittings on the top of the tank in place of the metric fittings we have had on the legacy engines. This may have been the time they also did the concave bottom plate inside the tank. Since I have had both style tanks (and installed the new engine in favor of the legacy metric fittings and flat bottom plate while the new tank is now a paperweight) I inspected and measured up the innards on both. In addition to the concave bottom plate, Rotax also extended the oil pickup tube which now dips below the rim of the concave bottom plate. I don't know their reasoning; but, with the new design, a liquid seal will exist between the pickup tube and small pool of oil contained in the concave design if a person drains the oil but does not pull the top off.

Rotax has always been adamandt that oil systems be purged to avoid sucking up air in the oil system; and, speculatively, the change may be relted to this. The are other ways to introduce air into the oil system, but the new design may cut one of those introduction points out.