Dear Vladimir,

Hope you're well. You're the second to report that upper shock mounts need to be "shaved" to install smoothly. I suppose that's better than having an under-sized mounting, which could "rattle".

As to penetrating oil, it could take several days for the oil to do its job. The oil weakens the corrosion bond as it percolates through through micro-channels in the corrosion. That takes time. Before trying to loosen a bolt in place for a decade or so, I saturate the bolt with PB Blaster (or Kroil, or similar) once daily for several days. When ambient temperatures are low (below, say, 70⁰F (15⁰C)) even more time might be needed.

Hope this helps.

Yours faithfully,

Spook