Differential drain Plug Types

Today I changed the differential gear oil in my 05 330Ci convertible with automatic transmission. The car has a little over 58,000 miles and we are the 4th owner. As I didn't know IF or WHEN the fluid had been changed other than when the car was produced, I decided to do it and ordered 2 plugs - the type with the integral green o-rings.

When I took the existing drain and fill plugs off the differential, both were the type with the integral o-rings. The production date of my car was April 05. If the differential oil had NOT ever been changed after production I guess I would have thought the plugs would have been the type that had the flat aluminum sealing washer INSTEAD of the type with the o-rings.

Would the fact that the plugs on mine DID have the o-rings would that indicate that a previous owner likely DID have the fluid changed OR could the OEM plugs at the time of production been the type with the integrated o-rings?

I'm just trying to determine IF a previous owner DID get the fluid changed say at 30,000 miles maybe.

Any thoughts? Gear oil looked very clear - amber color - not dark at all.

Thanks

Mike in Alabama

Differential drain Plug Types