I haven't tried it, but Brad Dimmock, a long time Colorado river guide places plastic sandwich bags in the oarlock socket. His claim is, no more squeaks. The need for this become obvious on multi-day desert river trips. Most lubricants draw sand which then increases the diameter of the socket or whatever is the softest.
Brass, oil impregnated bushings should be great, no need for sand collecting lube.
Rick N