Thank you @bbf2530 for the response! Yeah, The main reason is cost. The new 235/45/18 tires are costing me around CAD 1250, But I found someone who is selling hardly used 225/45/18 tire for CAD 800. Tires are good in good shape. So before making the decision wanted to understand if it's safe or not.
Some more information:
Its Winter tires, Continental VikingContact 7.
Load and speed rating is 95T where as my fusion's recommended load and speed rating is 94V.
With this full info, Do you think it would be safe to use that tires?