We saw today a few of our Bell Facebook friends posting pictures of new snow on the ground, up where they live in Colorado. Across much of the nation, the cold weather is either here or soon to be arriving. Diesel users know that this means they need to start arming themselves again cold weather problems with a good diesel anti-gel additive.
Diesel Fuel Gelling Is Worse With ULSD
Diesel fuel properties will change in cold weather. Diesel fuel itself is a complex mix of all different kinds and sizes of carbon molecules - some straight-chain, some cyclical, aromatics, aliphatics, all sorts of chemistry names can be applied. Included in this mix are paraffin wax molecules - wax molecules tend to be very heavy and complex. In normal diesel at normal temperature, the waxes are happily dissolved in the diesel fuel and burn right along with everything else, thus helping to provide some of diesel's energy value. But when it gets cold, the wax becomes undissolved and the fuel clouds up. This is the first step - the cloud point - towards the fuel gelling up. As the fuel gets colder, more of the wax "drops out" of solution, the wax crystals bump into each other and stick together (becoming larger). This process accelerates until enough wax is in the fuel that it will clog fuel filters and shut the engine down.
ULSD, specifically, gels worse than diesel fuel from ten years ago because of the way it's chemically treated at the refinery. Refineries are required by law to remove most of the sulfur from diesel fuel, down to leaving just 15 parts per million sulfur content. The methods they use to do this ("hydrotreating") make the now-ULSD fuel more easily gelled in cold weather. Bell's research has shown that ULSD is harder to treat for "cold flow" properties than diesel fuel from ten years ago, because of this change to the fuel.
Speaking of Cold Flow Treatment
The only way to keep diesel fuel flowing in cold weather, apart from mixing it with kerosene (which is frowned upon in all but the coldest environments) is to add a cold flow improver. Cold flow improvers keep the wax crystals from sticking together, so they stay small and pass through fuel filters on their way to being harmlessly burned with the rest of the fuel. A good flow improver like Cold Flow Improver will give you an extra 10-20 degrees of safety net, so your truck doesn't shut down or refuse to start in cold weather.
The only caveat with Cold Flow Improver products is that you have to add them before the fuel gets cold. These essential treatments prevent problems from happening, but they don't reverse a gelled fuel once it's passed it's gel point. To do that, you need Quick Thaw.
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This post was published on October 26, 2012 and was updated on February 4, 2016.