To make the mojo marinade, use a blender or food processor to mix garlic cloves, chopped onion, dried oregano, salt, pepper, cumin, grapefruit, lime, orange juices, vinegar, and olive oil. Blend until the garlic and onions are finely pureed. Keep aside 1 1/2 cups (360 ml) of the mixture to use as sauce and use the rest to marinate the pork.