Short story: Downtown 350 has 30,000km on it. Decided to add injector cleaner (PEA based) and ran it for a full tank, approximately 300km. When doing random cold engine oil check I noticed the oil, despite originally being 15W-50, lost viscosity and was almost watery. Looking at many other forums this is a known phenomenon, in fact some manufacturers recommend changing the oil after using fuel injector cleaner.