You might see a little less timing adjustment but I believe the fa20 engines are capable of using sub premium fuel so using premium fuel would only give a little advantage.
You might see a little less timing adjustment but I believe the fa20 engines are capable of using sub premium fuel so using premium fuel would only give a little advantage.
With the sensitivity to knock that these engines have, the ECU jumps at each and every opportunity to pull timing... even with 93 R+M/2 US gas from what I've seen. In that case, there would be definite advantages to running the most det-resistant fuel available.
But seriously... what does the manual say? Follow Subaru's guidelines. It may be regionally dependent.