What results has anyone had with gas mileage and power increases using Royal Purple motor oil.....I just changed my oil and decided to try the Royal Purple ---The truck appears to be better running espescially at the low end and I am seeing almost .5 mpg better compared to the 10.1 mpg i have been getting for the last couple months ----Has anyone seen similar results....my driving habits have changed in the last couple days -I hit the pedal harder...