I'm a fan of Synthetic oil, I change the filter each year and top the oil off, after a few years I will drain it, I found in the cold winter temps my hydros don't labor when starting, the oil flows like it should, not like syrup, and I can buy 5qts of Mobil ! at Wal mart for $26, good reg oil is $3.50-4 a qt so it's not that much more.
But with that being said, a oil change and new correct filter is best. no matter what brand or type you use, but I can't say use ATF over motor oil, I use what it calls for, just my brand and type.