After three months or every 3000 miles, one needs to put about a few drops of light oil or lock lubricant on door hinges and latch assemblies found on trunks, hoods, and doors. Additionally, there should be slight application of grease on the door latch strike surface to ensure regular sliding in place. As for trunking (or lift gate) as well as door locks, they may be sprayed with a graphite-based lubricator.