i dont know if they are or not, but i've added some vanilla extract to diet coke and it's pretty good. i'd assume they would. with lemon coke they started out as single 20 oz. bottles - regular caloric formula. then they came out with 2 liters, and then 6 pack of 20 oz, and then finally diet. that's how it happened in my area, anyway. I live in the northern chicago suburbs, and we have it, but we don't have surge around here. do they have diet surge? i love that drink.