for grins, i decided to submit an oil sample from my locked up 2.5L to blackstone for analysis. This is the motor i blew at the track two years ago. i strained the oil through a sieve to get any big chunks of metal out of it. here is the text of their result:
This oil may have been in use a long time, but wear metals don't look any worse off for it. Universal averages show typical wear levels for this type of engine afer about 4,800 miles on the oil. This oil was in use a little longer than that, but wear metals were nice and low, which is a good sign that all is well mechanically in this Boxster. Physically, the oil looks fine. The additive packatge was nice and strong and the trace of fuel isn't a concern. No coolant or other harmful contaminants were present. Air and oil filtration were fine. Nice report at 140,000 miles.
so what does this mean? to me, it means that none of the aftermarket M96 preservation techniques would have done anything to prevent this. the oil didn't suffer any viscous breakdown from high temps. the bearings were not starved for oil. the sump didn't run dry. the motor didn't overheat. there was no d-chunk or coolant intermix.
this failure was sudden and fatigue driven. this supports our initial guess: this was a rod bolt failure (or blackstone didn't actually analyze the oil, but i've used them many times w/ good results & trust their work implicitly). teardown this summer will confirm the failure mode.
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