On my last comment I should have also mentioned that I come from the Boating world mentality and go by hours. Lots of sitting in traffic where I live.
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The turbo is powered (spun) by exhaust gases which are extremely hot. The turbocharger has bearings that allow the impeller to spin at high RPM’s which draws In air used to pressurize the combustion chamber. The bearings are lubricated by the engine oil. The oil is critical to the life of the turbocharger. This is why you see a lot of owners myself included, that will change the oil sooner than the 10,000 mile interval specified by Toyota. This is why the OCI is related to the turbo. Hope this helps.
Turbos are cooled both with engine oil as well as the coolant/anti-freeze circuit.Wouldn't that already figured by the Toyota design engineers when they recommend 10k OCI? I'm sure they didn't want the truck to fail early.