Cold weather diesel

We were dreaming of a white Christmas here in Florida but we knew we weren’t going to get it. We did get an 80 degree one, though. This stands in contrast with much of the rest of the country that was (and may still be) shivering in the grips of a major cold snap. A polar vortex started freezing the country even before mid-December was upon us.  So if you lived anywhere in the lower-48 states besides Florida and some parts of the Gulf Coast, you likely were cursing the frosty cold winter weather.

Most drivers don’t worry about what the cold weather might do to their gasoline.  Unless there’s severe water contamination, gasoline doesn’t freeze up. Gasoline also vaporizes more easily at lower temperatures than diesel fuel does, which is the essential property the fuel needs to burn within an engine.  Diesel fuel is different. Its high wax content leads to terrible gelling problems in winter weather, as certain of its hydrocarbon constituents become less soluble when the fuel cools down. 

This forces diesel drivers to consider switching to “winter diesel” or “cold weather diesel” or some other diesel fuel with a similar name. The intent is to minimize the chances of diesel fuel gelling that they know is a possibility with conventional diesel fuel in the winter.  But what’s the real difference between cold weather diesel and normal diesel fuel?

Some people surmise that difference concerns the diesel fuel being processed differently at the refinery, kind of like winter gas vs. summer-blend gasoline. It’s well known that the composition of gasoline changes as the seasons change.  As the weather warms up in the spring, refineries produce gasoline that vaporizes a little less (to cut down on the millions of gallons of gasoline that are lost to evaporation with fueling). Later in the year as the weather cools down, they change the gasoline composition to make it more volatile (since you need that extra volatility and vaporization for the gas to function properly in the engine in cold weather).

Cold weather diesel fuel doesn’t refer to this practice. Rather, it refers to diesel fuel that’s treated with a cold flow improver. Some fuel distributors will provide this kind of diesel fuel as a pre-treated offering for their customers. If your fuel distributor does not, don’t worry. It’s not difficult to do it yourself and there are some quality cold flow improver options out there.  Whether you buy the diesel fuel pre-treated or do it yourself, it’s essential that the cold weather diesel fuel already have the cold flow improver in the fuel before the temperatures get below what the fuel’s cloud point is defined at.

In other words, in order to stop the fuel’s wax content from gelling, the cold flow improver needs to already be in the fuel when the wax starts to thicken up.  A good cold flow improver will contain multiple ingredients to keep wax particles from sticking together, to keep them dispersed, and to keep them suspended in the fuel so they don’t settle out as easily as they normally would.

Cold weather diesel is something you overlook in the winter time at your peril. Head off problems by making sure your diesel fuel has the right cold flow improver to make it a true cold weather diesel fuel.

You may be interested in these posts about winter issues:

• Cold weather engine problems for diesel
• New diesel advances mean more cold flow problems
• Newer Common Rail Diesel Engines Could Mean New Cold Flow Problems