2002 Tahoe, 5.3L, 213K, doesn't burn oil. Manual says 5K for oil changes using conventional 5W-30 oil, which is what I've done for the past 150K since owning it. If I were to start using a full synthetic oil could I bump the change interval to ~7500 between changes? Car gets about a 50-50 mix of city & highway driving. Appreciate your thoughts.