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Diesel Fuel and Cold Weather: What You Need to Know

Four fuel pumps with one for gasoline and one for diesel

Modern diesel engine technology makes starting a vehicle in cold weather much less of a challenge than it once was. Yet, when temperatures drop below freezing, diesel-powered vehicles suffer the same fate as their gasoline-powered counterparts: They’re simply harder to start. Preparing your car for extreme cold is important to ensure you’re never stranded.

Here’s what you need to know about diesel fuel and cold weather.

How Do Diesel Engines Work?

Unlike gas engines, which start when spark plugs ignite gasoline fumes, diesel engines rely on air compression alone. Typically, that compression is sufficient to raise the temperature in the combustion chamber high enough that the fuel ignites spontaneously. So, there’s usually no need for an ignition system to create spark. But in cold temperatures, diesel engines use glow plugs to raise the compression temperature to a level high enough to start the engine.

Heated glow plug pulled from diesel engineThe first glow plugs took 60 seconds to fully activate. However, by the 1970s, sheathed glow plugs lowered that starting time to 17 seconds, which still seems like a long time to wait to drive.

Modern automotive diesel systems are sophisticated, relying on turbochargers and glow control modules located in the cylinder heads to start vehicles immediately. As long as you follow the manufacturer’s maintenance guidelines, you shouldn’t have any difficulty starting your vehicle in moderately cold conditions.

Treating Diesel Fuel in Winter

Extreme cold, however, is the enemy of all motor vehicles and requires vehicle owners to take extra precautions. If you can’t shelter your vehicle when the temperature falls below zero, use a battery warmer, an oil warmer or a block heater to keep the engine warm. You’ll likely need an extension cord to connect to a household outlet.

You should also add a diesel fuel conditioner with anti-gel, which drops the freezing point of diesel fuel. Add this product to your fuel tank as soon as temperatures fall below freezing. Then, continue to add more each time you fill your tank, especially once subzero weather sets in. This conditioner will make it easier to start your vehicle, particularly when warmers and heaters are not available, like when you’re away from home.

Preparing Your Fuel System for Winter

Besides using the appropriate heater or warmer and utilizing a fuel additive, you should also test the health of your vehicle’s battery using a multimeter. The voltage should measure between 13.7 and 14.7 volts when the engine is running. If the readout is below 12.6 volts, replace your battery.

It might also be time to replace the glow plugs, which are usually externally accessible. Once again, use a multimeter to obtain the glow plugs’ resistance readings, which are measured in ohms. The acceptable range for the true resistance value is between 0.1 and 6 ohms, but consult your owner’s or maintenance manual for vehicle specifications. Replace faulty glow plugs as necessary.

Your Road-Ready Diesel

Your modern diesel-powered car should have no difficulty withstanding the worst that winter can throw its way. As long as you prepare for winter and follow all other maintenance recommendations, you can expect trouble-free driving year-round.

Check out all the fuel and emission chemicals available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on diesel fuel and cold weather, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Pixabay.

Matthew C. Keegan View All

Matt Keegan has maintained his love for cars ever since his father taught him kicking tires can be one way to uncover a problem with a vehicle’s suspension system. He since moved on to learn a few things about coefficient of drag, G-forces, toe-heel shifting, and how to work the crazy infotainment system in some random weekly driver. Matt is a member of the Washington Automotive Press Association and is a contributor to various print and online media sources.

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