Heat the oil in a saucepan over medium-low heat. Add the garlic and onions and cook for 5 minutes, stirring, being careful not to burn them. Reduce the heat to low. Add the ketchup, molasses, brown sugar, chipotle peppers, vinegar (or less to taste), Worcestershire sauce and salt and stir. Allow to simmer for 20 minutes. Taste after simmering and add whatever ingredient it needs (more spice, more sugar, etc.).