Are you getting your oil from the same place everytime? Different oils have different frost and gel points. Safest would be to get same jars and have different ratios in them, 20%, 30%... If the 80% started to get cloudy when cold, it would be time to go to 70%, ect. At least that is what I am going to do this winter. Most of last winter, I ran about a third bio unless it was getting near zero without a probem. Did use Diesel Clean once it was getting down into the teens... Also plugged in @ night.

I run mine throught 10-5-1 micron sock filters after distilling out Methanol and washing with Magnesol, then pump through an absolute filter. Need to update my gallery so I have better pics.