Does a Bigger Tire Size Increase Gas Mileage?. Part of the series: Troubleshooting Car Problems. A bigger tire size on a car doesn't increase gas mileage because it essentially is going to make the engine work more to get the vehicle to move. Find out why big tires may be beneficial on the highway, but not in town, with help from an ASE-certified mechanic in this free video on fuel economy and car tires.
