Well, today started the car with GC for the 1st time in "cold" weather...here it was 28 F. (I'm not counting the first start just after putting GC in, it was about 55F) during the first 5-10 seconds after starting this morning there were some "metallic" noises that I hadn't heard before, and I felt a steady vibration(wouldn't call it knocking) through the steering wheel. the motor seemed to idle a little higher than normal, and perhaps a little noisier. then, after about 10-15 seconds everything settled down(rpm down to normal)...I don't know what to think..normal/good/bad? the car started on the 1st try like always, but "sounded" a little rough at the turn of the key.(I didn't drive the car today, though, just strated up to see how it goes) Perhaps I should just give the motor a little time to get used to GC?? Has anyone experienced similar starts with GC at the beginning? However, the tapping/rattling noises I had heard almost all the time at idle with Chevron 10/30 dino seemed clearly less. tomorrow I'll drive and see how it feels. I guess I should try not to worry too much and trust the green elixir, and see what happens. Any suggestions/thoughts are thankfully welcome, especially from GC gurus.