Today I did not have time to warm up the engine. I had to pull out of the garage and go because I was on a surprise timeline to meet someone. I did not get on it, but I did put it in sport mode so I could hold the RPM range between 2 and 3K. The rattle was there for sure. The closer to 2K even, was the worst noise/vibration and got better if I was above or below. Once up to temp, it subsided significantly. Driving back after about 20 minutes, it was not noticeable. Guess it's what everyone else is saying, that it is the cold (even though "cold" is probably 75 degrees), block vs warm block and the pistons staying more consistent in size. We'll see if the Ceratec helps it at all, then going with 0 or 5W30 next oil change. Haven't decided on that yet. 5W certainly has more options available, but I've got time to do some more research before the time comes.