Actually I believe that I drive this vehicle in a rather conservative manner. I drive 150 miles daily to work, nice easy freeway miles, with few around town miles between commutes. This vehicles' automatic transmission does not appear to have fluid coolant lines to radiator. As a result I don't feel that there is a transmission cooler in use as is the case with most vehicles. Bear in mind that I live in Central California where the ambient temperature will stay in the three digit range for most of the summer. This vehicle receives average to better care. The only repair that I feel went beyond periodic maintenance, would be the replacement of the drive axles at 142,000 miles. Aside from this the vehicle has presented no problems and the transmission has functioned quit well aside from a few shifting quirks. Currently the Amsoil tranny fluid is neither brown nor does it smell burnt. I was unaware that Amsoil was felt to be a Marvel Mystery Oil like product, when I started this post. None the less, I am much more satisfied with it's performance/longevity than I am with the Hyundai OEM fluid