At What Temperature Does Diesel Freeze?

Winter is officially here, bringing with it the freezing temperatures some of us dread and some of us love. If you've ever wondered whether your car will start in the cold or whether your diesel might freeze, stick around to learn more.

First, there’s no one-size-fits-all answer. Like many things, the answer depends on a few variables:

·         Does the diesel have additives?

·         Is it biodiesel or straight diesel?

·         Is it blended?

·         Is the vehicle stored indoors?

·         How old is the fuel?

Rather than diving into all those individual factors, let’s start with the basics. Over time, we'll continue sharing articles with more detailed information.

Stages of Diesel Fuel Gelling and Freezing

Cold weather can significantly impact diesel engine performance. Here's a breakdown of what happens as temperatures drop:

1) It Starts with Icing Issues

Diesel gelling or freezing doesn’t happen all at once. It usually starts with water in the fuel. When a diesel engine runs, hot fuel returns from the injectors to the cooler tank, causing condensation. Improper handling or certain climate conditions can also allow water to seep into the tank. As temperatures fall, this water begins to freeze, triggering fuel problems.

2) Diesel Cloud Point

Paraffin wax, which is naturally found in diesel, helps with lubricity under normal conditions. But as temperatures drop, it begins to crystallize. When diesel reaches its cloud point, it appears cloudy due to the formation of wax crystals. While drivability isn’t immediately affected, these crystals can begin to restrict fuel flow and clog filters.

3) Cold Filter Plugging Point (CFPP)

As crystallization increases, flow becomes further restricted. Once the fuel reaches its Cold Filter Plugging Point, the wax buildup clogs the filter so much that the engine can no longer pull fuel. This is the lowest temperature at which diesel can still flow without obstruction.

4) Diesel Gelling

At around 10°F or below, diesel fuel can fully gel. At this stage, it solidifies and can’t move through the fuel system, rendering the engine inoperable until the fuel re-liquefies.

Summary

Understanding how diesel behaves in cold temperatures is crucial for anyone operating diesel-powered equipment or vehicles during winter. It all begins with water in the fuel and escalates through stages of wax crystallization, filter clogging, and eventually full gelling.