During the cold snap last week, when temperatures were around -5C, we had a few problems with the fuel waxing. We temporarily solved it by blending it with thinner fuels. Both Kenny and I ran our cars last week on roughly 70% waste soybean oil and 30% fossil fuel. It runs very well on this and I suspect it only needed about 10% dino juice. This is the first time I've had to resort to this since I bought the car in 2007.
I was caught out by the difference between the waste soybean oil and clean rapeseed oil, which we had tested previously in cold weather. I am making a few improvements to my fuel lines and thinking about switching to rapeseed oil during cold weather.