Correct binding or sticking door lock cylinders or keys that are hard to insert by applying the proper lubrication. Refer to Fluid and Lubricant Recommendations in Maintenance and Lubrication.
DO NOT use penetrating lubricants (such as GM P/N 1052949 and WD-40®). These lubricants wash out the original lubrication and eventually evaporate, leaving little or no lubricating material.
Important: Do not damage the painted surfaces.