I'm in the middle of a road trip from Cleveland Ohio to Pawtucket Rhode Island in my 2008 Mazda5. Drove over 600 miles with no issues. Then the last 50 miles I noticed the trans began downshifting not just on hills but even normal road inclines and I had to accelerate harder to get up to speed. The roads were level until about the last 150 miles traveling through the Berkshires with many up and down grades. Plus its been 90 degrees. No dash lights. I checked the fluid level and it seems full, even over-filled. Fluid isn't black on the district and doesn't smell burned. I just bought the car a few weeks ago and am wondering if the used car dealer put in the wrong fluid? Wondering if I do a drain and fill by disconnecting the line at the cooler to get all the fluid out including from the torque converter and refill with fresh correct type fluid, if that might resolve the problem...at least to allow me to drive home 650 miles?