place the 8 pounds pork shoulder into a roasting pan with the fatty side up. Puncture the surface of the meat with a fork. Mix together in a small bowl, blend minced garlic, salt, pepper, oregano, adobo seasoning and olive oil. Rub the paste into the punctures of the meat. Cover with plastic and store in the refrigerator overnight. Preheat oven to 350 degrees.Remove the plastic wrap from the pork shoulder and replace it with aluminum foil. Cook for 3 1/2 to 5 hours, checking the meat every 30 minutes after the 3 1/2 hour mark. Remove the foil when the pork is nearly done and allow to cook for another 20-30 minutes to become crispy on the surface.