Thanks. This is really useful info.
I guess Mazda is not concerned if the source of the oil around the exhaust impeller is coming from the crankcase through the PCV valve? That would produce the same oil on the exhaust impeller, would it not?
I guess Mazda is not looking at the turbocharger oil return line size, a known source of excessive pressure on turbo bearing seals in many different brands of high performance turbo engines when that return line is undersized.
I would have thought they would have the tech first check to see if there is any oil on the iinside of ntake tubes to and from the intercooler. Quick, simple, inexpensive thing to check. If they are oily, then it's more likely to be unburned crankcase fumes passing through.
If those tubes are dry and the turbo exhaust impeller is oily, then the TSB starts making sense. But disconnecting the "precat" (the DP) is a pretty major service procedure. Most of us would just rub our index finger back and forth inside the exhaust tip and see if the "soot" is oily. Maybe that's just too simple or not sufficiently diagnostic.
Assuming the turbo is replaced, I'm left wondering whether the issue will come back and am wondering if there is some actual change in the design of the replacement turbo.
