waiting for winter

O.K. so the temperature has dropped below 0°C (32°F), once in the last few days. Not to panic, since it's still oktober and lower temperatures are yet to come. Am thinking of mixing a little petrodiesel with my biodiesel since antigelling additives that I mixed with my biodiesel didn't make any difference.
I put 5 times the amount of antigelling additive that you would normaly put in petrodiesel, but it hardly made any difference. So now I'm thinking of mixing this biodiesel that is treated with the additive together with petrodiesel , at a mixture of 50:50 (B50).
Because I added 5 times the amount of additive, It should make a difference since it would bond with the petrodiesel.
I mixed in 1 litre of additive with about 150 litres of biodiesel, so now I should add 150 litres of petrodiesel. Hm, I use 100 litres of fuel per month , so that should get me through 3 months of temperatures lower than -10°C. But the question remains - at what temperature does this fuel become to thick to get through the filter?
I quess I'll have to go out and make some tests. Sorry to say that I should have gotten petrodiesel last winter (it's pretreated to withstand temperatures down to -20°C). Now I'm gonna have to mix in summer petrodiesel.