what will cause a loss in gas mileage?

Hello, That may be the case, but have the vehicle tested first. An exhaust gas recirculation (EGR) valve that is stuck open can cause the same issue, as can a dragging brake caliper. These are just a couple things that are possible, not to be considered a to do list. Have it test driven and scanned by a technician to identify the cause.

There are multiple power train components that could cause your existing problem. Such as vacuum leaks, timing components or even a sensor related problem. We at Holly Tire would be more then able to diagnose your poor acceleration problem. Please feel free to call and set up an appointment for us to take a look. Thanks, Holly Tire & Auto Service 248-634-9011