yar, the API did not come up with the MT-1 rating to satisfy the ignorant masses. It is a rating of gear lubricants required by Eaton/Fuller and Meritor for use in their class 8 non synchronized truck transmissions. It is not meant for passenger or light truck transmissions. I have been using API MT-1 fully synthetic 50w in my Fuller and Meritor transmissions for about 20 years.
