The WVO might have cleaned your injectors up a bit, and maybe lubed everything up in there nicely. In the four vehicles I've converted, I have not noticed any running quieter, but they all run different. My truck idles almost 200 rpms faster on WVO, and seems to better on #2 as well since I made the switch. Maybe my tired injection pump can pump it easier or something, since I definitely know that the WVO has less energy than diesel.
I converted a '97 Dodge (12 valve cummins) and an '85 Mercedes that both idled about 100 rpms slower, which was explainable due to the lower energy content in the vegetable oil. Both of those motors have really robust injection pumps (maybe weren't as affected by the different fuel as my truck is).
Dad's PSD doesn't run a bit different on either fuel since conversion.
With my truck idling higher ,and therefore a bit smoother, on VO I figure it must like its high fat diet better.
