Hello all. I was getting a consistent 26 mpg with my '07 mazda 3 HB. I drive with and without my carpool partner, use the ac periodically, and drive a mix of freeway and surface streets. At 1/2 tank the odometer USED TO show 150 miles. Now for the last 2 months I am lucky to get 115 miles at 1/2 tank. About the only thing that has changed is the weather. It has been really cold lately (34 deg) in the morning. The car runs fine overall. Any ideas as to what could have caused a drop in mpg? Thanks

 

You might be experiencing what winter time mixed fuel does.
Many parts of the country, especially in the colder climates are adding up to 10% methonal during the cold months. Since alcoholcarries oxygen in it's molecules, it is only 66% as efficient as gasoline by volume. The car will run leaner andto compensate, the ECM/PCM adjusts by adding more fuel to the fuel/air mix thereby reducing fuel mileage.
That may be your problem, especially since in many states they are not required (litigated) to post the ethonal/methonal content at the pump.