You might be asking yourself why I’m talking about exhaust leaks as a possible cause of poor MPG. The reason has to do with how your engine calculates a fuel mixture after it warms up. After your engine warms up, it goes into what is referred to as “closed loop.” This means that your computer is taking information from your O2 sensors located in the exhaust stream to calculate the fuel mixture. Any exhaust leaks near an O2 sensor can throw off its readings. When this happens, it can upset your fuel mixture, thus compromising fuel economy. So if you have poor MPG and exhaust leaks, you might want to address those as part of your effort to get better gas mileage. Here’s a video you might find useful if you’re looking for exhaust leaks on your vehicle.