Just came from Napa and noticed that GTX 5W30 bottle looks and costs the same as a conventional but is now labeled a synthetic blend. After reading some posts here and asking the Napa guy it seems that most if not all 5W 30 oil is now, or for several years now, a synthetic blend. Most people agree that switching a 300,000 engine that has only seen conventional to full synthetic has a good chance of introducing new oil leaks. Is there a chance that using the new blend standard will have the same problems that a full synthetic could have? Is it better to go up to the 10W 30 that is still labeled conventional? Is all this blend no blend labeling just marketing/legal issues where the oil inside is still the same? Since the blend bottle looks and costs the same as their conventional I am thinking it is made by the same processes.