[naz]

aka and 2001 ZTS.. for what it is worth.. i actually geeked out and trolled bobistheoilguy.com and the maintenance section of nasioc to look for used oil analysis reports. IMHO this is the only way to get tech on oil. additives remaining lets you determine how long you can extend the drain interval, viscosity test tells you if the oil is indeed too thin, and wear metals tells you if the oil is protection

many analyses of mobil 1 'energy conserving' products (5w30 and 10w30) do show they do not have good high temperature shear stability (ie they shear down to a 20weight). in my personal opinion, this is too thin for the WRX because this means the oil is below the 5w30 recommendation of the OE

i posted a number of my oil analysis on here... i have used shell rotella T 15w40 and it worked great in my motor. very low wear metals, awesome additive package and extremely shear stable

i also used 'german castrol' 0w30 (apparently one of the 'gold standard' full synth oils) and it too protected my engine well (no better than the rotella though)

if anyone tells you an oil is 'good' without showing you a used oil analysis report for the specific application you are discussion, nod and smile and make a mental note that person probably thinks anecdotal evidence is a great way to 'bring the tech' to a discussion