Hi, was trying to put my bike into my back garden and had to hold the bike up on one wheel to get it through the house. While I lefted it up some dark black oil came out the back. I don´t know what oil it was and was wondering if anyone could help me? I know if it was engine oil, riding the bike without enough could be serious. I´m not even sure if it was engine oil. Hope someone out there knows lol my manuel is in German. I´m British. Look forward to hearing from someone lol