Although Hyundai claims 100K service on 2017 Sonata 6 speed automatic transmissions - I don't believe that is a good idea not to do drain & fills sooner on a vehicle you plan on keeping past 100K miles (i.e. debris in ATF , fluid oxidation , etc.) Therefore I plan to do drain & refills every 30K miles (once I figure out the 6 speed , no dipstick , semi - sealed , drain and refill directions) . *Question is - what is the current SP 4* synthetic ATF Hyundai is making for 2017 6 speed automatic transmissions ? Next , I hear Hyundai ATF is not exactly the greatest ATF to begin with - what is a better brand ATF with Hyundai approvals ? Lastly , I don't want some sketchy "designed to meet / multi vehicle ATF" which may or may not work ... Your suggestions and experiences for a very good Hyundai approved ATF which is a good value and is cost effective ? Thanks in advance !