In a small bowl, mix the mayo, yogurt, vinegar and spices.
Add oat milk, a little at a time, until you reach the consistency you prefer. Use as a dip or dressing.
Video
Notes
You can also make this using my dairy-free ranch seasoning mix. Add 2 tablespoons of the seasoning mix to 1/2 cup vegan mayo and 1/4 cup vegan Greek yogurt. Add a splash of lemon juice and season with salt and pepper. Add plant milk to thin it to a dressing consistency.