Yes wet cleaning will remove it and yes it was oil. It is not the higher resolution of the D7000 - it was visible when looking at the sensor - and very clearly oil when all of the "dust" particles smudged exactly where they were as lines of yellowish oil when looking at the sensor. After that was cleaned, it happened again, and without any attempt at cleaning my father took it to the store where he bought it. The employees at the camera store and the technicians at the Nikon service centre all agreed that it was oil. Apparently this is not the first D7000 that had been brought in because of this. There is a very clear difference between dust and oil. I experience dust on my D200's low pass filter. My father had oil on his D7000's low pass filter. I clean my D200 with the exact same techniques. They have worked every time for years - because I have only ever had dust on the D200 sensor.
You may have not have had oil on your D7000, but my father, some Nikon service techs, some camera store employees, and I all agreed that his D7000 had oil on the sensor filter.