I know everyone has their favorite brand but what exactly should I be looking for? I have never owned a turbo car and just recently bought a slightly used Chevy HHR SS with a direct injected 2.0L. GM recommends Mobil 5-30 in the manual. I think that is what is in it now. I know GM is pushing change intervals really far. Right now I am at 18% oil life (no idea how many miles). The turbo seems to whine a bit more loudly when the oil is cold (below freezing). It seems to be oil temp related and goes away within a minute of driving. Any opinions?