Strange piston deposits?

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Jul 17, 2010
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This is from a BMW S54 engine with 94k miles. I just bought it 3k miles ago. The engine looks reasonably clean under the valve cover so I think it's had regular oil changes. Not sure what's going on here though. Any thoughts?


piston2.webp
piston3.webp
piston4.webp


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Looks like antifreeze (coolant). Head gasket leak.
I'm not sure if it's coolant. I don't think I'm losing any, plus S54 almost never leaks coolant into the cylinders being closed deck with wide spacing to the coolant openings, and I see this on all 6. Also, my last UOA showed no signs of coolant.
 
It just appears to be a small amount of ash from the lubricant’s additive package. What is the SAPS level of the oil that you are using?
1.29% for Castrol Edge 10W-60 according to 2021 PDS. I don't run Edge, I run the BMW TPT 10W-60 which should be around 1% but most of these engines have run the Castrol for the bulk of their lives.
 
Weird. It almost looks like aluminum oxide, l
It just appears to be a small amount of ash from the lubricant’s additive package. What is the SAPS level of the oil that you are using?
Ash, but I doubt its from the add pack. The engine would have to be burning oil like its fuel to leave such deposits, I'd think.

Seems to me it's likely to be fuel-related. Perhaps the previous owner preferred a local station that he thought was reputable but turns out the fuel wasn't good.


Coolant consumption sometimes looks like this too because of the silicates and phosphates in some coolant formulations. Glycol itself shouldn't leave much of anything behind when burned (it's a hydrocarbon and it WILL burn!).
 
Maybe its my old eyes, but could this be wear instead of deposits? Almost looks like cavitation. Could this be minor LSPI?
 
Weird. It almost looks like aluminum oxide, l

Ash, but I doubt its from the add pack. The engine would have to be burning oil like its fuel to leave such deposits, I'd think.

Seems to me it's likely to be fuel-related. Perhaps the previous owner preferred a local station that he thought was reputable but turns out the fuel wasn't good.


Coolant consumption sometimes looks like this too because of the silicates and phosphates in some coolant formulations. Glycol itself shouldn't leave much of anything behind when burned (it's a hydrocarbon and it WILL burn!).
One thing to consider is that it’s a Z4M so it’s a fair weather car and probably has been stored for long periods since it’s a 2006 MY car and has 94k miles. Bad gas could be a possibility.
 
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