just did the first schedualed oil change in our 2010 frontier and switched to amsoil high performance synthetic. before the change i was getting 15.5-16 MPG's city driving and now with the amsoil i am getting 17.5-18 city. i am pretty impressed, amsoil said there would be an increase in mpg's but i didn't realize it would be that great. the other thing is amsoils high end synthetic oil doesn't need to be changed nearly as often as conventional synthetics but i am worried there may be a waranty issue if i don't follow nissans maintenance recomendations, even though amsoil says their oil doesn't void waranties