Piano hinges get contaminated by glue, epoxy, paint and old-fashioned dirt. When I reinstalled the nose gear covers the hinges were so stiff that the spring would not push the doors open. I found the best lubricant was _not_ LPS-3, graphite or petroleum-based. I got a better, cleaner result using "Lightning Dry Lube", a product made for bicycle chains. The lubricant is a Teflon powder and the medium is a mineral spirit. The product wicks along the pin, so application is a very small amount applied to the piano hinge's interleaving spaces.