Grease, oil, butter and fat are al the same when it comes to dealing with the stain.. They are stains that can be dealt with quite easily in numerous ways.
General laundry advice is to soak the item in water with your usual detergent prior to washing at the maximum temperature that the fabric will allow. Any remaining stain can be removed with any household grease solvent. Grease solvents are washing up liquid /dish detergent, household soap or white spirit. You can also but a multitude of commercial grease solvents. In the UK they have names such as Dabitoff or Swarfega.
