This study assessed the effects of vehicle mileage on the floor panel geometry and the upper mounting of the McPherson struts, as well as on the wheel alignment parameters. Geometry changes were determined in cars with the same design parameters, differing only in the type of engine supply system. The cars were van-bodied vehicles with compression ignition engines fuelled with diesel fuel and spark-ignition engines fuelled with LPG. The vehicles differed significantly in the weight distribution on their axles. The study is distinguished by its comprehensive approach to identifying in-service body wear. A detailed analysis covered not only the main causes of changes in body geometry, namely the influence of the vehicles’ mileage and design parameters, but also the effect of identifying the values of changes in the suspension and steering system geometry parameters. The body geometry and wheel alignment testing was carried out at a mileage of approximately 300,000 km. The study determined the relationships between changes in body geometry and wheel alignment. Changes in body geometry were determined by the type of basis point and the type of vehicle under analysis. Major changes in body geometry and wheel alignment were found in diesel-fuelled cars at the front of the vehicles and in LPG-fuelled cars at the rear of the vehicles. The greatest changes in body geometry in both vehicle types were noted within the area of the points associated with the mounting of the front and rear axle suspension system components.