A pair of eights should always be split in blackjack. Splitting eights gives you a better chance to form two strong hands, especially since 8 is a relatively weak card, and splitting it creates two chances to improve your hand. Whether the dealer shows a strong or weak card, splitting eights is generally considered the best strategy. The only exception would be if specific table rules (like no splitting) or certain strategies dictate otherwise, but in most cases, splitting eights is the optimal move.