Handle Fuel with Care

Don’t be your fuel’s worst enemy—keep it clean and dry

You put it in the tank, and the engine runs. When the fuel runs out, you put more in. The engine runs. Things keep going like this, until one day … the engine doesn't run. What happened? Of course, there are many possible reasons. But your fuel could be the problem. It's so easy to take your fuel for granted, but it's possible that it's gradually creating a major problem for your equipment. Do you really know the quality of the fuel you use? Do you store your own fuel on site, but take its quality for granted? You shouldn't. Here's a look at diesel and gasoline fuels, and how to maintain fuel so your equipment keeps on running.


In addition to sustaining combustion, diesel fuel lubricates and cools the fuel injection components of the engine. To protect these precision-made components from wear and damage, use only clean, high-quality fuel of the correct grade.

The American Society for Testing Materials (ASTM) has adopted certain grade standards to identify different diesel fuels. Each grade of fuel will meet the needs for certain engines in certain operating conditions. Most power equipment manufacturers consider only grades 1-D and 2-D satisfactory for use. Grade 1-D is more volatile than 2-D. Most manufacturers recommend 1-D for cold temperatures, wide variations in load, frequent speed changes, long periods of idling with low load and high altitude operation.

Grade 2-D is recommended for warm ambient temperatures, heavy load, high speeds and lower altitudes. The requirements are often conflicting, making selection difficult. Follow the operator's manual for the specific equipment.

Cetane number

Cold starting, warm-up, roughness, acceleration, carbon deposits and exhaust smoke can be affected by the ignition quality of the fuel, which is measured by the cetane method. The minimum cetane number specified by the ASTM for both 1-D and 2-D is 40. The engine manufacturer may suggest fuel with a higher cetane number at low ambient temperature and high altitude. Check with your fuel supplier for availability of fuel with higher cetane ratings.


The engine manufacturer often specifies limits of sulfur, water and sediment in the fuel. Usually these are within other regulated limits for fuel sold commercially. However, you must be sure that the fuel still meets these standards by the time it is injected into the combustion chamber.

Improper storage and handling will contaminate good fuel. Diesel 1-D contains some sulfur and water. Combining the two can form sulfuric acid, which will etch metal parts. Condensation of moisture in diesel fuel storage tanks occurs more easily than in tanks for gasoline because the more volatile gasoline vapors provide some resistance to the entrance of moisture-laden air. The moisture condenses inside the tank and the water droplets then run into the diesel fuel.

Fill equipment fuel tanks at the end of each day to reduce air space for condensation. Allow enough time for water and contaminants to settle, then drain water traps at the beginning of each day. Inspect fuel filters often and change them before they become plugged.

Do not store diesel fuel in galvanized containers because the fuel may dissolve the zinc coating, which can then remain in solution until deposited in the pump or injectors. Fuel additives often contain alcohol or another solvent that can dissolve plastic parts. Use additives with extreme caution—only after considering the engine manufacturer’s recommendations.

Cloud point

When the temperature is cold enough, diesel fuel forms wax crystals that will not pass through injectors. The temperature at which the crystals form is identified as the cloud point because the fuel will appear cloudy. Use fuel with a cloud point at least 10°F (12°C) lower than the lowest anticipated ambient temperature to prevent plugging of the filters in cold weather. Some additives can be safely used to lower the cloud point, but use caution and follow the manufacturer's guidelines. Never add alcohol or gasoline to diesel fuel as an aid to starting in cold weather.

Diesel storage

Store diesel fuel carefully to protect it from contaminants, using large, permanent storage tanks wherever possible. Maintain these permanent storage tanks carefully, and filter the fuel from these tanks as it is transferred to equipment tanks.

Water requires a long time to settle to the bottom of diesel fuel, so the fuel must stand 12 to 24 hours after filling or moving before the water can be drained. If possible, use two storage tanks—one for active use while the new fuel is settling in the other. If you have one storage tank and are expecting a fuel delivery, fill the equipment fuel tanks before the supplier fills the storage tank.

It is best to fill equipment fuel tanks from rigidly mounted storage tanks that are properly installed, maintained and filtered. Observe the following precautions:

  • Don't let water, dirt or anything else collect on top of the storage drums.
  • Don't let the fuel-transfer-pump suction pipe extend to the bottom of the storage container.
  • Don't ever transfer fuel in an open container.
  • Don't knock dirt into the equipment tank while filling. Clean the cap before removing it.
  • Don't store diesel fuel in a galvanized container. The fuel reacts with and dissolves the galvanized coating, later depositing this material in the filters and the engine.
  • Don't store diesel fuel in containers that were previously used for gasoline or other solvent unless the containers are carefully cleaned. Fine rust and dirt, which will quickly settle out of gasoline, will mix readily with the diesel fuel and cause damage.
  • Always drain sediment from the fuel storage tank before transferring fuel.
  • Always use a filter between the fuel storage tank and the equipment tank. Drain the water trap and service filter as suggested by the manufacturer.
  • Always cap the transfer hose nozzle when not in use to prevent the entrance of moisture or dirt.
  • About twice a year (spring and fall are suggested), thoroughly drain and clean the storage tank. Rinse out loose sediment with clean diesel fuel.
  • Use smaller containers to transport fuel between the storage tank and the equipment. Steel drums or similar portable containers require special attention to prevent contamination of the fuel. You can be sure that if there is dirt and water in the containers, it will be completely mixed with the fuel by the time you reach the equipment. Therefore, make sure the portable containers are clean before filling them.


No one purposely puts dirt into his or her gas tank, but that is exactly what can happen every time you add gasoline to your equipment. Your fuel can pick up contaminants during shipping or when stored over 60 days, handled improperly or left in unsuitable containers. The most common invaders are rust, dirt and water.

Large storage tanks, metal gas cans and fuel tanks are the starting points for rust's invasion. It forms, over time, when fuel levels (primarily in metal containers) remain low and condensation exists. Rust is an abrasive and can damage your entire fuel system.

Dirt and water invade your fuel in several ways. Dirt is mainly introduced to fuel through dirty tank spouts and dispensing funnels. In addition, dirt and debris may invade your fuel whenever you remove a dirty fuel cap. Dirt is a real danger. It causes gasoline to deteriorate, clogs fuel lines and destroys engines. Water also can enter your fuel by various routes—the most common being condensation. In less-than-full metal tanks, warm, moist air condenses on the cooler inside wall of the tank. Before long, droplets of water mix with the fuel, not only causing deterioration of the gasoline but also of the tank itself—thus inviting rust.

General storage recommendations

By storing your fuel correctly, you protect your equipment and help prevent invasion from unwanted, damaging contaminants. Gasoline breaks down over time. These five precautions will delay this deterioration:

  • Use approved storage containers.
  • Fill containers to only 90 to 95 percent capacity.
  • Cap containers tightly.
  • Store containers out of direct sun.
  • Purchase your fuel from a reputable source.

When conditions require you to store your power equipment for 90 days or longer, add a fuel stabilizer. This will keep your fuel fresh. You can purchase additives at auto-supply stores and some service stations, in addition to your equipment dealer. Follow the label directions. You achieve the best mix when you first add the stabilizer to the container, then add gasoline. The stabilizer works only when you add it to fresh gasoline—it cannot restore deteriorated gasoline.

Equipment preparation

Most equipment manufacturers recommend that you not store equipment for extended periods with gasoline in the fuel tank and that you empty the tank and run the engine until the fuel line and carburetor are empty. Both recommendations aim to protect fuel-system parts from gum deposits. While most gasoline is stable beyond 30 days, it's best to defer to the recommendations of the equipment manufacturer—especially during the warranty period—when it comes to storage. Follow the fuel and storage recommendations in your owner's manual.

Many equipment managers prefer to use a fuel stabilizer instead of completely draining the fuel tank and lines. The draining procedure poses a number of challenges. First, it is virtually impossible to get every drop of fuel out of the system via draining. You need to blow out fuel lines to ensure they are dry, because any remaining fuel can cause problems. Second, draining the fuel exposes the metal tank and fuel system to air and moisture, which, together, result in corrosion and rust, as well as dry, cracked and shrunken gaskets—which cause fuel leaks.

Detecting deteriorated gasoline

Gasoline deterioration occurs in three ways: Evaporation, oxidation (gum formation) and contamination. Moderate deterioration by evaporation or oxidation is virtually impossible to detect without testing. However, testing by a qualified laboratory is impractical except where a large amount of gasoline or a critical situation is involved.

  • Evaporation. Evaporation of some volatile components is impossible to detect without testing. Only specialized laboratories can run these tests. Look in your Yellow Pages under laboratories to find one near you.
  • Oxidation. Severely oxidized gasoline has a rancid odor and darker color. Do not inhale the fumes purposefully. If you notice a foul odor, follow this test procedure: Fill a jar with the questionable gasoline. Shine a light through the jar, examine the color, look for separation and look for contamination particles settling to the bottom. If the color is abnormal and debris is visible, discard the gasoline. The presence of solid gum particles also results in the loss of brightness and clarity. Testing is required to detect moderate oxidation. Perform all tests on gasoline outside or in well-ventilated work areas.
  • Contamination. Common gasoline contaminants are dirt, water and rust. Visual inspection reveals all of these contaminants—even water. However, because they tend to settle, sample from the bottom of the container or fuel tank.

Handling gasoline safely

We have all read cautions about gasoline, but these warnings change, and we require updates. Take a minute to refresh your knowledge about these precautions. You certainly do not want to risk an accident. Simply put, gasoline is dangerous. First and foremost, it is highly flammable. It is easy to ignite, and it burns explosively. Second, exposure to gasoline—in liquid or vapor form—can adversely affect your health.

The seemingly simple task of filling a container requires precautions:

  • Use only approved containers.
  • Shut off the engine.
  • Place the container on the ground at a safe distance from your vehicle, equipment, other customers and traffic.
  • Keep the nozzle in contact with the container during filling.
  • Manually control the nozzle valve—do not latch it open (If the nozzle has a fume-collector, the filler-spout seal must be compressed to activate the dispenser.)
  • Do not smoke.
  • Avoid breathing gasoline fumes.

Flowing gasoline generates a static electric charge that builds up on the gasoline in the receiving container. If the charge has no opportunity to dissipate, it can discharge to the metal spout of the dispenser nozzle as a static spark. If the spark occurs near the open mouth of the container—where the concentration of gasoline vapor and air is in the flammable range—it could ignite the gasoline. Never fill a container in the trunk of a car or in the bed of a truck (especially a truck with a bed liner) because the static charge dissipates more slowly and is more likely to ignite.

Putting the container on the ground and keeping the nozzle in contact with the container helps dissipate the static charge.

At most, you should fill the container to 95 percent of its capacity. For example, if the container is 10 inches tall, leave 0.5 inch (5 to 10 percent) of air between the surface of the gasoline and the top of the container. Gasoline, like any liquid, expands as its temperature increases. In some parts of the country—during certain times of the year—stored gasoline may encounter 50°F temperature swings. A 50°F temperature increase causes gasoline to expand approximately 3.5 percent. If no air space exists for this increased volume, the gasoline will escape via the container cap or vent. Also, the walls of the container will distort or crack, perhaps causing a spill.

  • Handling gasoline away from the service station. To avoid a fire, keep gasoline away from any ignition source—such as a welder or grinder. For safety reasons, you must not store or handle gasoline within 50 feet of any appliance pilot-light system or igniter. Gasoline fumes, which are invisible and heavier than air, travel along the floor where air currents do not disperse them. When they ignite, fumes act as a fuse that conveys flames back to their liquid source.

To avoid eye and skin contact, wear safety glasses and gasoline-resistant gloves. For fire and health concerns, handle gasoline outside. Fewer ignition sources exist and fumes dilute and disperse more readily outdoors.

Disposing of gasoline

  • Non-deteriorated gas. To avoid wasting fuel, you can store excess, non-deteriorated gasoline in the tank of your equipment along with the proper amount of fuel stabilizer. Store any additional gasoline in an approved (preferably plastic) container (90 percent full) and add a fuel stabilizer.
  • Deteriorated gas. It is not easy to dispose of deteriorated gasoline. However, companies that specialize in this task can help you do so in an environmentally responsible way. Finding your best alternative may take some research. Sources of information include your community's fire department, recycling center and hazardous-waste disposal center. Check the government pages of your phone book to locate these organizations. The Yellow Pages contain listings of commercial disposal organizations under environmental and ecological services, oils and waste. Paying for this disposal is better than the price you will pay for replacing an engine you have damaged by using inferior gasoline.

An alternative—one that is practical only for smaller amounts of gasoline—is to mix the old gas with newer gas in small proportions. For instance, 1 gallon of older gas in a tank of 20 gallons is sometimes recommended. A 20:1 ratio ought to sufficiently dilute to prevent the older gas from harming the engine. However, be sure that age is the only problem before you do this. Gasoline contaminated with dirt, or large amounts of water or other contaminants should be disposed of rather than used, even in diluted form.

Technical credit: Robert Mills and Robert Sokol, Technical Manuals Division, Intertec Publishing Corporation (Overland Park, Kan.).

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