The car may have different size tyres front and back, but Michelin does now do Cross Climates in 225/40 R 18 92 Y; 235/45 R 18 98 Y and 245/45 R 18 100 Y. If they match your sizes you can fit them and leave them on all year round, benefiting from good performance in snow and mud, better ride quality, less tyre noise and no penalty in fuel economy or tyre life. But don't overinflate them. Run them at the lowest recommended cold pressures.