I've been using synthetic every since I got rid of my 1993 nissan maxima. I changed the oil on it, and you can see where some of the oil was thick and almost sludge like. I replaced that car with a 2001 Acura TL and since then I've been changing my own oil using synthetic every ~6k miles (figured it costs twice as much as regular oil, might as well go only twice as long). I replaced the TL with a 2008 G35 and the G35 with a 2010 Escalade which uses synthetic from the factory. All of them use synthetic from day 1 with zero issues. but the awkward way GM mounted the oil filter, and how the oil drain plug is sideways, i bring it to the dealership to change now. Charge me 100 bucks every time.