Why did my gas mileage drop

Hi - Dave here, contributing to RepairPal and providing expert advice since 2010. Fuel economy is based off of real world conditions. It is hard to know what software update, you are speaking of, and what it would have affected. But fuel, air, spark mixture must be proper for proper engine performance. If it means you lose a little bit of fuel economy because the engine needs to run properly – then I guess that is what it At the same time, your vehicle is 10 years old. Have filters been replaced? Have spark plugs been replaced? What kind of driving habits are occurring? In Citti? Highway? It's too difficult to figure out without more specific information. The best suggestion I have is to get with a local shop near you to drill down a little further. https://repairpal.com/auto-repair-near-me Click the link to find some shops near you who can help out!