I used to monitor my gas mileage with every tank and found it to fluctuate very little from 21.5 mpg - so I stopped monitoring about 8 months ago. The last 3 tanks I have been quite surprised to be getting 16.8 mpg! I drive in Southern California, always burn premium gas, and have noticed no change in the cars performance.
Any suggestions as to what has caused this sudden 20+% drop in mileage.
Thanks