[wmjosiah]

After changing the oil filter and reading a bunch of forum posts about how this is a VarioCam solonoid seal, and how maybe the motor is designed in such a way that perhaps that seal isn't even needed, and driving it several more thousand miles, with that noise occurring less and less frequently, and in the last few thousand miles, not at all, I feel it necessary to post an update: This isn't happening at all anymore, and hasn't for several months and several thousand miles. Just letting the seal disintegrate and letting the motor get all of the seal-bits out of its system appears, at least so far, to be a valid course of action. The car runs normally, doesn't make any untoward noises, doesn't burn any oil, gets normal gas mileage, and is still an absolute joy to drive. I'm sure this isn't the "right" course of action, but for a $7000 car with 170K on it that doesn't appear to have any symptoms at this point, I'm just going to leave it alone unless I notice any further problems.