OK, Gearheads. I need some help figuring out what's going on with my '05 CC. For over four years now, I've been averaging 16-17 MPG, daily driving. In the last few weeks, it dropped to barely 14 MPG. Driving conditions and habits haven't changed. If anything, I'm using less right foot than before to see if that will bring the MPGs back up. Cleaned the air filter. Checked the pressure in the tires. Recent services included rear differential and an oil change. I switched to Pennzoil's High Mileage stuff. Could that be it? I'd appreciate your feedback. Thanks.