Motorcycle Repair: 1991 1200 sportster recommended oil, diesel engine oil, hd oil

Question
what is the best oil to use in my 1991 1200 sportster crank case and how much will it hold w/ a new filter

Answer
Mike, use any good quality 20/50 oil.  It must say V-twin air cooled motorcycle oil.  Motorcycle oil is a higher grade than what you use in your car.  It's closer to diesel engine oil because diesels operate at much higher temperatures.  Just use Harley oil or Spectro or Drag Specialties or any big name brand but make sure it says V-twin motorcycle oil.  Use the harley filter and three quarts of oil.  If you run in hot conditions or stop and go you might want to use full synthetic oil like the Harley Syn-3 or Mobil-1 vtwin mc oil.  Again, use the 20/50 synthetic.  It's $9.00 a quart for the HD oil.  Use the HD "Sport Trans" oil in your primary/gearcase.  One quart even.  And no matter what oil you use, you should change it every 2500-3000 miles or once a year if you don't put that many miles on in a season.