It can be easily made oil free (and actually uses very little oil anyway). When sauteeing the onions and garlic, just use a bit of water instead of oil. If you BBQ or grill the sausages then you don't need any oil. You also can bake them oil-free using a silcone baking sheet (affiliate link). If frying the sausages, you can use a spray bottle (affiliate link) filled with olive oil to massively reduce how much oil you use.