The rinse phase of the ARX treatment on my Ford Focus Wagon (78000kms) 4 cyln is almost complete. Had no oil leaks or anything unusual show up except for very dark oil. So I'm hoping since everything went well, I'm done with the ARX treatment. Now for the great part. I'd love to put synthetic oil in this car, for all it good reasons and for it's better cold weather starts up. And I want to use the green elixer of life. I just want to make sure that GC 0w30 is okay to use on this Ford that has "5w20 oil only" stamped on it's oil filler cap.