why does it differ so much? like a average oil weight for asphalt is like 35 but a average for carpet is more like 60wt! its just a diffrent surface why do you need to that much more heavier of a shock oil?
But remember, TOO stiff will cause the car to skitter. It's unlikely given that most parts are tuned to avoid this, but if you set it up for carpet and try it on an asphalt track, you'll see more than a little of this.