I don't really know if heavier oil would have the exact same effect but I doubt it. I use the steel spacers supplied by Race Tech, just cut to the recommended length. I used all the recommended settings from Race Tech thinking they would know better than me. They seem to work fine for my weight (approx 170 -175 lbs) and riding style (I love corners). I have used PVC before in other applications. I think it is schedule 40 (whatever is the thickest one). Be sure and use washers on each end of the spacer. Every bike I have owned for the last 25 years or so has had Progressive springs and other mods to the forks. My last two bikes got Race Tech springs which seem to not dip as badly when braking as Progressive. I used to add heavier oil also but have gotten away from that in recent years. Seems to slow fork response (but it is all subjective).