I ran syn in the WRX I had for a long time. It was Mobil 1, the filter is more important than the oil IMO. I'd run the crankcase to 10k but change the filter about every 3000. No problems ever like that.



Bypass filters are where it's at. They filter down to what, 2-3 micron? Full flow do 19-23 mic at best... so you're REALLY keeping it clean with a bypass. Not to mention increasing the total oil capacity.

Do a full flow with a bypass section on the ATF too... stock "filter" is a screen that filters down to 100 micron only!