Gary Wilcox wrote:

When I bought the plane the pre-buy inspection was a complete annual and the
mechanic didn't mention any "aluminum in the oil" so apparrantly this just
started.

If the previous owner changed the oil and filter just before your pre-purchase, there
wouldn't be any particles in the filter for your A&P to find. Check the engine log
book. Assuming that an oil change was made and that the change was properly logged,
you'll know whether it just started or not.

What is the likely source of this aluminum?

Don't know that one. Most of the critical components such as bearings, cylinder
sleeves, wrist pins, etc. are not aluminum. I'd say that's encouraging. If I had to
guess, I'd say that a bearing is loose and eating away at it's housing, but that
usually makes a good deal of noise.

The mechanic suggested that I
fly for 10 hours and change the oil again to see if the problem goes away.

Stay close to home.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.