Winter Starts All the Way Through Summer- Mitsubishi Service said Nothing was Wrong?

[Top_Fuel]

The tires are different and do have an impact on mileage...

Remember that nothing has less rolling resistance than a worn out Low Rolling Resistance tire. So even if you replaced your tires with a new set of OEM Enasaves, you would still notice a slight reduction in your fuel mileage.

You didn't mention what tires you are using. If you bought some off-brand tires that aren't Low Rolling Resistance, that could make a significant difference.

I know this sounds crazy...but you aren't driving around with your automatic climate control on all the time, right?

If there is something wrong with your car (like a bad coolant or air temperature sensor), this could have a significant impact on fuel mileage. There is a reading in the car's computer called "Fuel Trim." It's basically a reading that indicates if the computer is being directed to use more (or less) fuel than usual. You can read more about it here:

Fuel Trim as a Diagnostic Tool

A good tech would have looked at your fuel trim. A tech who's only getting paid 30 minutes of warranty time to look at your car may have just looked for error codes.