As per Phil's recommendations. Mine had the black gloop in and only about a tablespoon of the stuff came out.
I jacked the rear wheel off the ground so it could be run in gear to warm up, flushing out with diesel 2 or 3 times and then cheap 20-50 engine oil. This was continued until the oil coming out was as clean as it went in.
Have used Millers EP140 every year since with no problems or leaks, and like Phil's it seems to be getting quieter.
1 ltr of oil does about 4 oil changes.
Best of luck with it.
