I currently run RP in my motor. I was looking at RP web site and it has a different line of oil they call in their HPS series. Has anybody used this series and if so have you noticed a difference in performance, idling or anything else? Thanx in advance.http://http://royalpurple.com/motor-oil-HPS.html

 

I think the HPS is like the regular RP used to be, SL rated w/ higher zinc and anti wear additives than newer SN motor oils. Now the standard RP is rated SN so they changed the formula, and the HPS looks like it is formulated like the old SL royal purple but w/o the SL rating b/c it costs money to get the API starburst put on oil.