Redline's price is about on par with other high end oils. Amazon has the 75w-140 for about 14 a quart now. Not bad, considering RP is about 18 and M-1 about 18 for that viscosity. It really quieted the diff down, especially low speed backing and highway cruise. I have stock exhaust, so I can hear power train noise. But this summer, watch out, Magnaflows are going in!