I have used AMSOIL in many vehicles with great results. I used the Signature series oil with their oil filter and observe the 25,000 mile/ 1 year change interval. I have found that my mileage actually increased by using this. My 37 foot motorhome with chevy 454 went from 6 1/2 to 7+ with nothing more than changing the oil. If I change the transmission fluid should increase even a little more. My Kia Sedona gained about 1+ mpg when I changed and it was a high mileage vehicle when I got it. I drive lots of miles ( average 3000/ month ) as a courier, about 30% interstate 70% city. So far on my 2015 has an average of 44.3 mpg with normal driving.