So, since the hive mind here has seen things I've never seen... And without getting into the silliness of over-analysis due to oil sampling... yeah, yeah... we know... Our O-470 has consistently shown slightly elevated aluminum (around 20ppm) for 5+ years. So... anyone else ever seen slightly elevated aluminum for years and years on oil analysis? Very consistent. For numbers, we've seen as high as 38 (hmm) on one oil change back in 2013, and our "unit average" from Blackstone is 16. Their "universal average" for this type of O-470 is 7. Last time we were at that average was 2011. Other maybe pertinent details, maybe not... if you have other questions, ask... If I know, I'll answer. - Engine is about 1200 hours. O-470-S. - Prop was overhauled quite some time ago. We had some minor "spitting" of oil from it four or five years ago which after following the SB from the manufacturer to "deep cycle" it once in a while, stopped completely. - Oil changes run anywhere from 20-35 hours depending on our schedules. Average runs about 25 is the idea. Probably ran closer to 30 the last four years. - Chrome cylinders. - No appreciable oil burn (Maybe a quart in 30 hours...) - Definitely some small oil leaks that haven't been hunted/found, but always a little oil kinda "everywhere". (Blackstone also said this could be case spalling and a leak at the case half seals...) - We do run CamGuard but not sure if we were running it in 2012 when this was first seen. Don't think so. - AeroShell 15W50. Anything else y'all have seen on low-compression big Continentals and aluminum? Figured I'd ask. Like I said, Blackstone says nothing they're concerned about. "...the high aluminum reading is not inconsistent with past samples, and since all the other wear metals look fine, we're not too concerned about aluminum at this point. When aluminum is the only element out of line like this, it often shows something like case fretting or even an aluminum dipstick. Look for oil leaks along the case halves." Aluminum dipstick is a possibility... feels lightweight, and it looks shiny... that's about all I know about the stupid thing. LOL. Maybe we play with our dipstick too much?