Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Radius
PRIM_OILTANK_RADIUSParameter: Height
PRIM_OILTANK_HEIGHTParameter: Height Segments
PRIM_OILTANK_HSUBParameter: Cap Height
PRIM_OILTANK_CAPHEIGHTParameter: Cap Segments
PRIM_OILTANK_FSUBParameter: Rotation Segments
PRIM_OILTANK_SEGParameter: Switch to Updated Oil Tank
PRIM_OILTANK_SWITCH_TO_UPDATED