It's also worth pointing out that climate has a big effect on turbo engines. I believe we are running an air to air heat exchanger which are very efficient, but they have limitations. Your engine's air inlet temperature will always be a few degrees higher than the outside air temperature. If you live in the northern states or Canada your engine will run much cooler and be happier than the same engine in the southern states or Mexico. Cold air is more dense than hot air and has more oxygen molecules packed in it, so cold air not only makes the engine run better but it makes a little more power. If you live in a hot climate I would run 91 octane all the time and do more frequent oil changes, but if you live in a cold climate your probably fine with 87-91 octane and running closer the recommended oil change intervals. It's also a good idea to add a bottle of fuel injector cleaner every 3k miles or so to clean the combustion chambers. Direct injection is very efficient, but also notorious for fouling up. The high pressure injectors can't self clean like the older injectors because they are inside the combustion chamber vs being in the intake manifold so they experience high heat and pressure while the older ones did not.
Steve
