diff --git a/frontend/src/views/RecipeManager.vue b/frontend/src/views/RecipeManager.vue
index 1057e8e..3ca66d8 100644
--- a/frontend/src/views/RecipeManager.vue
+++ b/frontend/src/views/RecipeManager.vue
@@ -864,6 +864,13 @@ function filteredOilNames(search) {
 }
 
 function selectOil(ing, name) {
+  // Check for duplicate oil in current recipe
+  const existing = formIngredients.value.find(i => i !== ing && i.oil === name)
+  if (existing) {
+    ui.showToast(`已有「${name}」，请直接修改滴数`)
+    ing._open = false
+    return
+  }
   ing.oil = name
   ing._search = name
   ing._open = false