Peter wrote:
zero renters, and zero schools … who remain as clueless on operations as ever and continue to spread scare stories about leaning.
You know that’s not true.
I didn’t write that quote.
easy to get into false positives
Can you give an example? I have not seen one. Short of really way out numbers, there are few “positives” in oil analysis. It’s a trend thing.
BlackstoneLabs wrote:
I think operational factors are going to have more of an effect on how much metal shows up in analysis. But even more than that, you might be seeing aluminum from the case itself. Any time the engine sits idle you can get moisture that collects on the case, and that causes oxidation. The oxidized aluminum washes into the oil when you start the engine, and voila! Extra aluminum. It might be worth looking at your aluminum values vs. hours on the oil and the time it took to accrue those hours. We consider anything less than 5 hours a month to be inactive, though of course that will vary depending on climate.
High aluminium is probably one of the less important things. You can get elevated “soft” metals just by having a hole in the air filter, or by the alternate air door not closing fully.
Peter wrote:
you could be chewing up some bearing (due to an oil gallery offshoot being blocked) really nicely and will never notice it on performance, not until the bearing is red hot, and there won’t be any metal in the filters because it is way too fine.
But if that happens, is it not going to happen quite soon after the bearing becomes oil-less? Thus unlikely to be caught by periodic oil analysis….. unless the period is every 15 minutes in the cruise.
As a Group/solo owner, there are big variations in engine usage.i suspect this would make oil analysis unreliable. I change oil at 25 hours, spin-on oil filter at 50. And do not fill to max, or allow down to minimum. O200 engine.
is it not going to happen quite soon after the bearing becomes oil-less
Not if the blockage is partial, which is very likely because what blocks these passages is dirt.
Don’t ask me how the dirt gets in, but one TB21 owner managed to get a non-functioning prop pitch control, purely by getting enough dirt inside the front of the crankshaft to completely block the oil feed to the prop. He never posted any details… – here.
This article from Mike Busch has just turned up in email. It contains an interesting snippet on metal potentially getting past the oil filter and ending up blocking the galleries feeding the crankshaft bearings.
However, how the hell can metal get through the oil filter, I have no idea. Perhaps gross negligence in running the same oil filter for years? Who does that?
