I used synpower 5w30 in my Dad's Ecotec 2.4, and it made it run more quietly than it ever did on any M1 5w30 or 0w30, or Super Tech Synth 5w30. BTW, MPG hasn't changed by using 0w30 M1, I knew the Florida heat would limit the effectiveness.
I used it in my 2.2 Ecotec and heard and felt no difference when compared to Q-Torque 5w30, PP 5w30, Havoline Synth 5w30, Super tech Synth 5w30, and M1 5w30.
I also used it in mom's Jeep 3.7 SOHC, and felt nor heard any difference between M1 5w30, PP 5w30, and Q-torque 5w30. Currently I run Q-torque 5w20 because I got 15 quarts for $1 each because no Advance Auto Parts buy trusted 5w20 synth! The engine is nosier, but MPG is up .5 in all conditions!