Slow Cooker Texas Pulled Pork

Ingredients

• teaspoon vegetable oil
• pork shoulder roast
• barbeque sauce
• apple cider vinegar
• chicken broth
• light brown sugar
• tablespoon prepared yellow mustard
• tablespoon Worcestershire sauce
• tablespoon chili powder
• extra large onion, chopped
• large cloves garlic, crushed
• teaspoons dried thyme
• hamburger buns, split
• tablespoons butter, or as needed