thought of this also, left old filter on after removing oil, filling with Pennzoil Ultra Platinum 5w30,,drove a few days ,noise on startup was gone with Pennzoil Ultra Platinum, then put on new filter & topped off slightly to full mark on dip-stick,, same brand and model (Purolator One,PL14617) specs for this engine, as by pass valve setting, verified by Purolator in relevance of Subaru specs, the ESP did make more startup noise and engine felt sluggish until warm ed up, then was ok, the Pennzoil Ultra Platinum 5w30 was much more responsive, and NO more clattering, the outside temps about the same to note. the slightly thicker running viscosity of the ESP may affect the VVT on this engine is what I think, as in regard to the Subaru 2.0 is spec to use 0w-16 which I am not a fan of the .0w20 will be used in winter time, as previously I used Pennzoil Ultra Platinum 0w20. Mobil 1 ESP did not work well, at least in this case, the euro oils are a higher viscosity but within the perhaps outdated J-300 chart which may need a bit of updating,,,,,,,,yes there are differences in API and Euro viscosity's ???. 0w-20 oils maybe more forgiving with this engine, note the Pennzoil Ultra Platinum 5w30 is of a lower vis. (thinner) compared to the higher vis ESP even though is claims 0w-30.