use existing add_carrier_buses function

scripts/prepare_sector_network.py

@@ -1556,24 +1556,7 @@ def add_land_transport(n, costs):
         )
 
     if ice_share > 0:
-        if "oil" not in n.buses.carrier.unique():
-            n.madd(
-                "Bus",
-                spatial.oil.nodes,
-                location=spatial.oil.locations,
-                carrier="oil",
-                unit="MWh_LHV",
-            )
-
-        if "oil" not in n.generators.carrier.unique():
-            n.madd(
-                "Generator",
-                spatial.oil.nodes,
-                bus=spatial.oil.nodes,
-                p_nom_extendable=True,
-                carrier="oil",
-                marginal_cost=costs.at["oil", "fuel"],
-            )
+        add_carrier_buses(n, "oil")
 
         ice_efficiency = options["transport_internal_combustion_efficiency"]