"Old English" is an aglomeration of Angle and Saxon dialects and and variations on a common base language. If there was a particularly distinct Saxon-specific language, the unfortunate truth is that we'd almost certainly never learn about it, but it helps to think of Old English variations between Saxons and Angles in the way that we might think of, say, Catalan and Occitan, or Danish, Swedish and Norwegian: distinct certainly in terms of dialect, but broadly speaking mutually intelligable.