I recently changed my oil in my truck and I put in RP HPS oil instead of their regular street oil, which I have used for the past 2 years. What I have noticed with the HPS is one I gained .2 mpg's, the other thing I have noticed is the "Hemi tick" was a little bite quieter with the regular RP street oil but my truck has more giddy up to her. It is not much more then before but I have definitely noticed a slight difference. My truck just feels a little more stronger then it did before the change. I have a little over 200 miles on the HPS oil and I like how my truck has responded to it plus I gained a slight increase in mpg's, I'll take that any day. I had ruffly 6100 miles on the old oil and I usually go longer on RP but I didn't want to get stuck changing my oil in the dead of winter with possibly snow on the ground.