The other day by mistake I went to the Marine shop and bought synthetic oil for the oil/gas mixture 50:1 ratio and it ran fine all day. I took it out tonight and it was fine on the way out but when I was coming in I had it about 30 when all of a sudden it sounded like the engine wound out and immediately stopped. I went to turn it over again and it started and runs but now I hear a grinding noise/ pinging at idle and when I try to go into gear it wont move? Does anyone know what this problem may be and if so could the different oil have caused this problem? All responses are greatly appreciated...