"Here's a couple things to think about. How about the ring land area or some oil passages not much bigger than a pin hole."
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I'd like an engine that's spotless as much as anyone else, and typically, my rides have had very light varnish and no sludge at all.
That said, I'm not sure why some folks assume that engines somehow aren't designed to handle small amounts of sludge or varnish, or conversely, that small amounts of S/V will likely damage an engine, or that it's an unacceptable abberation to have same in one's engine. There's been valvetrain and intake valley photos on this board that almost looked like they were covered in wet roofing tar -- you could barely make out the engine components -- yet the engines still ran (although poorly).
Andy: If you have a modest coating of varnish on your 210K mile engine, I'd call that perfectly normal. Not the norm for fans of this board, but certainly normal for the driving public. I'd also suggest that your level of deposits is not only acceptable, but EXPECTED by the powerplant engineers who designed your engine, with little or no impact on performance. After all, you EXCEEDED the manual's requirements regarding change-outs of your API-spec'd oil. There's enthusiasts on this board who'd suggest that an engine you couldn't eat off of, or internal components that didn't shine like chrome, are somehow "unacceptably dirty." None of this reflects reality, nor the Detroit/Tokyo/Munich engineers' expectations of how "Average Joe" will service his ride. Engines can typically endure a high level of abuse before damage -- let alone death -- and moderate varnish doesn't rise to the occasion.
If you desire to address the varnish (and why the heck not), you might try a reputable oil additive or go a cycle or two using a mixed fleet "diesel" oil -- these have especially high levels of detergents/dispersants, even more so than synthetics.
