I been using PENNZOIL ULTRA 5W30 for 1 year,it's works great .
I'm think next year try some t6 5w40 , and few days ago I went to CT and saw T6 also has 0w40 at same price
And I google it about put it in mazdaspeeds . But did not find anything .
Anyone in here using that the 0w40 ? Is it better at winter ?