I've been doing about a 50-50 to 70-30 blends and they are working excellently. The car loves it and actually sounds quieter and smoother on it. When I runout of WVO and go to stright diesel, I wonder for a few miutes if something is wrong with my car it sounds so rough, but then I remember that there's no oil in there! To filter I use a 2 step system based on danalinscott's designs. He's great and I highly recommend following his instructions if you are new at this, it will prevent any small mistakes that could ruin an otherwise easy and enjoyable experience. Are you talking about on board filtering? I do all my filtering before it enters my car, only leaving the tinyest amount to be dealt with in my standard fuel filter. I run it through a bag filter(which I make myself and it's really cheap and easy per the above mentioned plans) and then a polishing filter to get the remaining little bits. Good luck and I h ighly reccomend the bidiesel infopop web site for detailed info and no bullsht.