Are you letting the motor idle several seconds before shutdown? This is necessary to allow the turbo to cool and avoid oil coking in the hot center section. Even with that precaution, the oil cokes some, which is why you change the oil religiously at 2.5-3k mi on a turbo.
I agree 150%, I used to work on Mistu cars for an small shop that "specialized" in Land rover, Jaguar, Mercedes, BMW, and Mistubishi. Anyway, I replaced the turbos on several eclipses and two 3000GT VR4s. The problem was the use of cheap bulk oils, and not letting oil temps lower before shutdown. The oil would sludge in the drainback tube to the pan. Once the sludge would restrict the tube so far, the seals in the turbo would blow, causing a James Bond smoke screen effect. And just as fast, the catalytic convertors would stop up. Can you say,[color:"red"] catastrophic failure [/color] ? <img src="/forums/images/graemlins/ignore.gif" alt="" />
And expensive.
The sythetics out there are good in this case as they do not create mineral deposits like dino. This helps but not cures the coking. I use it in my non-turbo and I change it just like dino, every 3mo/3k mi.
I recommended it to the people that owned turbos and I never had a failure with it. Knock on wood. Synthetics are not a cure all. People treat them as such, and get a bad attitude about them when things fail. Will synthetic blacken in this case? Yes. Like I said, it helps, but not cures the problem. If you change your dino often enough it will be fine too.
