I recently purchased a Passion which I have now driven through a few fill-ups. The first tank of gas (all premium) I got 42 mpg. Then a couple at 38 mpg. Now, the last two I have gotten 30 mpg. I have been so disappointed. Any ideas?
How was the weather compared to those other two tanks? I'm thinking warm up idling possibly. Check the normal things like tire pressure too even though your tire pressure monitor should have caught it. Is your car brand new or used?
As posted elsewhere on this site, the first tankful may not be accurate as it may have been refilled with a few miles on the car. Almost every car tends to get lower MPG's during the break-in period. With Mobil 1 in the motor, the break-in period is a bit extended as synthetic oil tends to lubricate too well and does not give the rings a chance to wear in right away. Most people experience lower MPG until around 20,000 - 30,000 miles. some more, some less. Don't worry too much about it Get used to driving the car and the milage will get better soon.