One of my bikes has been sitting since December. Oil in it is Mobil 1 10-40 (bike oil), and it's only got about 1,500 miles on it. Should I dump it and replace, or is it okay to run? Also another question: if a bike has been sitting with used oil for a long time, would it be better not to run the engine to heat the oil up as usual, but dump the oil without running the engine first, then replacing with a cheaper oil, and then run the engine to heat the oil in order to be able to dump whatever nasty stuff is left over from the old oil? Thanks in advance.