Good point plank, but while 10p per litre doesn't seem that much cheaper, over a year it will add up to a substantial saving - I fill about 3 times per month, 60 litres per go, so £6 per fill, or £18 per month (based on current fuel prices) at the current ratio of 80:20. Increase the ratio of oil to diesel, and the saving gets bigger.
I'm noticing no change in how the wagon runs on an 80:20 mixture, in fact it is running better than the last time I was running it on biodiesel - better starting, less smoke. Obviosuly the use of petrodiesel is helping, but by starting at a low ratio an moving upwards it should be possible to judge if any running problems come in. I'm also not filling the tank, deliberate decision, to mean that if I get any running problems I can fill with petrodiesel to dilute the mixture further.