According to the Toyota oil chart, the 2003 Toyota Sequoia I have can run 5w20 (original spec 5w30). Normally, I run M1 5w30 and change every year or 7.5k. This vehicle is only used for long trips (>100mi) or towing the 3500lb boat 20 miles on flat terrain about 5 times a year. The vehicle has 120k miles. Since this vehicle is mostly used for interstate travel, would I see a significant improvement in mpg if I run 5w20 or even 0w20? Right now it gets 17.1mpg according to the digital readout. I've only seen 1 person run 5w20 in the same engine in a tundra running Valvoline and the 3 uoa showed about 1-2 ppm iron wear increase.