By Ed Thomas
September 2002

Low temperatures exacerbate any weaknesses your trucks may have, and one of the first things to feel an icy grip is fuel. Diesel fuel will cloud and gel when the weather gets cold, and crud can get into the tanks and lines, impeding fuel flow.

There are some simple preventive steps you can take, like buying quality fuel from reputable sources, using proven additives (and using them properly), and equipping your truck with a fuel heater and a fuel-water separator.

The fact is, you can trace most cold-weather fuel problems back to one source: water. Water will corrode and eventually plug a fuel line, or damage the sensitive and expensive parts within the fuel system, like fuel pumps and injectors.

Moisture in the fuel system is impossible to prevent. Water makes its way into fuel storage tanks at the dispensing point, and it most certainly forms inside your truck’s saddle tanks as they cool. Water condenses on the inside walls, then coalesces and puddles at the low point of the tank, beneath the fuel. If there’s dew or frost on your windshield, there may be dew or frost inside your fuel tank. So keep your tanks close to full, so the walls aren’t exposed.

You can’t stop moisture from forming in the tank, but a fuel-water separator can wring it out of the fuel before it gets to the injection system and disrupts or damages it. A good separator will meet Society of Automotive Engineers standards for removing emulsified water (tiny bits whipped into solution, as though mixed with the fuel in a blender), droplet or “plug” water (larger water droplets that are carried in the fuel but not emulsified), and dirt.

If you’re buying a fuel-water separator, ask to see the manufacturer’s data based on results of these SAE tests; if the maker can’t supply them, consider a different product.

The fuel/water separator should be installed at or below the level of the engine’s fuel pump to avoid air-locking problems. And the closer it is to the engine the better, because engine heat will help keep fuel flowing and water from freezing in the separator’s sump (freezing water is the number-one problem with separators). Some fuel-water separators simply remove water and rely on the engine’s primary and secondary spin-on filters, which remove dirt and other contaminants like algae and fungus from the fuel. They’re located on the block where engine heat prevents wax crystals from plugging the filter media. Other separator products act as filters, using specially treated elements to strip away water and remove contaminants.

Several spin-on filters have media that will strip most emulsified and plug water from the fuel, as well as remove solid contaminants. These may do a good job, but their capacity may be limited by the size and type of the media. This can be a problem with high-power diesels which use fuel at higher rates.

Double-check the filter complement to be sure it’s up to the job. Each engine has a published fuel flow rate-45 to 90 gallons an hour, generally-and filters should be able to keep up with the flow without restricting the rate or pressure. But be careful in adding too fine a filter-2 microns or less, which can restrict fuel flow at low temperatures as the fuel gets thicker. Difficulty in cold starting, or lack of power during warm-up may be due to a combination of very fine filtration and higher viscosity fuel resulting in lack of sufficient fuel flow to the engine to reach full power.

Keep it Hot
In winter, drivers keep engines idling so they’ll have heat in the cab. Running the engine also keeps the fuel warm, preventing it from gelling. But as a matter of company policy, some truck owners don’t allow extended idling, so heaters in the saddle tanks or on the fuel line are needed to keep diesel warm enough to flow properly.

Fuel heaters can be installed separately, in a filter canister, or be part of the fuel line itself. They usually cut in and out automatically. Using an internal thermostat, a heater typically switches on just above freezing and then warms the fuel until 30 C or so, when it will shut off to prevent overheating.

Heaters use electric current or hot engine coolant to warm the fuel. Either type has advantages and disadvantages. The electric type is simple, but on cold mornings draws current from the batteries, potentially running them down when you need their power to crank the engine. The coolant type works well as long as the coolant is warm enough; on a cold morning, it has no warmth to offer-unless you’ve got a block heater that warms the coolant first.

A good heater allows you to burn No. 2 diesel year-round, which delivers better fuel economy than No. 1 or a 1-and-2 blend (though you may not have a choice because refiners often thin-out fuel destined to be sold in cold climes). Mount it upstream of the separator so it benefits from warm fuel. Avoid elbows in fuel lines because these act as freeze points.

For extra protection, heated fuel lines keep all fuel within its length warm; sometimes these have a pigtail that extends into the tank, heating the fuel in there as well.

Bitter cold weather usually sends drivers to the counter of the truckers’ store, where they plunk down dollars for fuel additives. They all know that a good additive will keep their fuel flowing and them moving down the road. Some know it can do a lot more and that it can help in hot weather, as well.

Typically, fuel additives can do (or claim to do) several things: absorb water; kill biological contaminants, like algae that grows in water, or fungus, bacteria, and other crud that grows in the fuel itself; lower the “pour point” (the temperature where fuel begins to pour sluggishly in cold weather) and “cloud point” (when wax crystals begin forming); improve the cetane number, which is a measure of startability in cold conditions but doesn’t make the engine run any better (look for a cetane number in the mid- to upper 40s); and clean your fuel injectors and other critical internal engine parts.

If you use additives, mixing them in with fuel when it’s delivered is the surest way to control dosages. Otherwise, you’ll have to rely on your drivers to mix it properly as needed. Keeping printed instructions with bottles of additive in a convenient place inside the cab is not a bad idea, but don’t expect a driver to stand around in freezing weather and read them. Make mixing additives and fuels in general part of your regular driver training.

While there are many good products out there, some additives can damage engine components. Sharp managers write up a list of approved products and instruct drivers to buy only those on the list. If you’re an owner-operator, pick an additive with a brand name you know and trust and use the product according to directions. Typically, that’s one quart per 100 gallons of fuel. Don’t overmix just because you may feel that if a little additive is good, a little more is better. It ain’t so. Overuse can harm the engine or, at best, cause you to spend more money than needed.

If you buy the right fuel for the seasonal conditions, you generally don’t even need additives, says Andy Pickard, Petro-Canada’s senior advisor on fuels.
“In Canada, the common diesel fuel is seasonal diesel fuel, which is adjusted monthly by geographic region and is suitable for virtually all low temperatures in the region,” says Pickard.
In certain parts of Canada, truck stops will offer two “seasonal” fuels-one marked for local use and a second fuel for adjacent colder regions. Also, during abnormally cold snaps, some truck stops will switch their seasonal diesel fuel to a lower cloud-point product.

But not in most parts of the United States. Truckers travelling home on a backhaul should find out about the low-temperature properties of the fuel they buy down south to avoid waxing problems in Canada, where the winds blow colder and the temps fall a lot farther than any Yankee winter.

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