AdBlue, also known as diesel exhaust fluid (DEF), is a liquid additive used to reduce emissions from diesel engines. It works by converting harmful nitrogen oxide (NOx) emissions into harmless nitrogen and water vapor.

Most modern diesel vehicles with selective catalytic reduction (SCR) systems require AdBlue. Adding it helps diesel vehicles meet stringent emission standards and run cleaner. AdBlue is not a fuel additive but rather an essential fluid for the SCR system to function properly.

AdBlue is a clear, non-toxic liquid made of 32.5% high purity urea and 67.5% deionized water. It cannot be substituted with any other liquids. Using low quality or incompatible fluids in the AdBlue tank can damage expensive components of the SCR system.

Why Do Diesel Vehicles Need AdBlue?

Diesel engines operate at a higher temperature than gasoline engines, producing more NOx as a byproduct. NOx gases contribute to smog and acid rain, having an adverse impact on the environment and health.

SCR systems use AdBlue and a catalytic converter to significantly reduce NOx emissions from the exhaust. When injected into the exhaust stream, AdBlue breaks down NOx into harmless nitrogen and water vapor. Most modern diesel cars, trucks and heavy equipment now come equipped with SCR technology and require regular refills of AdBlue.

Without AdBlue, the SCR system would stop functioning properly, increasing emissions significantly. Most vehicles are designed to discourage drivers from running AdBlue levels too low, by limiting speed and power. This makes carrying and refilling AdBlue essential for diesel vehicle owners.

Checking AdBlue Levels

Keep a check on AdBlue levels at each fuel fill-up or at least once a month. Most vehicles have an AdBlue gauge on the instrument cluster, some show it as a percentage while others display it in liters. An AdBlue warning light may also indicate if levels are critically low.

Additionally, many diesel vehicles have AdBlue level sensors that estimate the driving range left before the tank runs empty. Pay attention to the warning messages and estimated distance/driving mileage you have until the AdBlue tank requires a refill.

Letting AdBlue run very low can allow NOx emissions to exceed acceptable limits, while completely running out will trigger limp mode - drastically cutting engine power as a warning for the driver to refill it.

Filling Up the AdBlue Tank

When the AdBlue gauge approaches low levels or refill warnings pop up, it's time to top up the AdBlue tank. Follow these steps for hassle-free refilling:

Locate the AdBlue Fill Cap

Unlike fuel, AdBlue has a separate fill cap, usually placed next to the fuel inlet. It is typically blue in color and labeled “AdBlue” or “DEF”. Make sure not to confuse it with anything else under the hood.

Purchase AdBlue

AdBlue is available at most gas stations and auto part stores, sold in bottles or larger containers. Prices can range from $8 to $25 depending on brand and quantity. Bulk purchases can save money in the long run. Make sure the AdBlue meets ISO 22241 standards.

Pour from the Bottle/Dispenser

Place a funnel under the fill cap if the opening is too small to pour from larger containers. Refill amounts will vary by vehicle - check the owner’s manual. Leave some room at the top for expansion in hot weather.

Replace the Fill Cap

With AdBlue refilled, replace the fill cap tightly. Double check that it is the AdBlue opening and not mixed up with anything else. Wipe away any splatter or spills before closing the hood.

Reset Warning Lights

Turn on ignition and start the vehicle. AdBlue warning lights should go off within a few driving cycles. The range/mileage estimate should also return to normal levels on the dashboard.

How Much AdBlue Do Diesel Cars Use?

AdBlue consumption varies significantly by vehicle model, driving style and conditions. On average, expect AdBlue usage around 2-3% of diesel fuel consumption.

For example, if your vehicle averages 40 miles per gallon of diesel, you would need around 1 gallon of AdBlue for every 150-200 gallons of fuel burnt. Higher fuel usage, frequent accelerations and cold weather can increase AdBlue consumption.

AdBlue tanks are also sized differently based on expected driving ranges. Passenger cars may hold 4-8 liters, while heavy-duty trucks have 20 liters or larger tanks. This means refill intervals range from every few months for light driving to every few weeks for high mileage users.

Consult your owner’s manual for exact AdBlue tank size, consumption rates and driving range estimates specific to your vehicle. Tracking usage for a few tanks can also help narrow down how often you need to top it up.

Shelf Life and Storage of AdBlue

Unopened AdBlue bottles or containers have a long shelf life of at least 18 months from production date, if stored properly. The fluid may last even longer before it starts to crystallize or degrade.

Check the expiry date on AdBlue bottles before purchase and use. If there are visible solid crystals settled at the bottom of old containers, do not use them as tank contamination can occur.

For storage:

• Keep AdBlue sealed in original containers out of direct sunlight and extreme heat. Over 90°F/32°C causes faster deterioration.
• Do not freeze AdBlue. Extreme cold below 12°F/-11°C will crystallize it. Bring to room temp before using crystalized bottles.
• Store in a cool, dry place ideally between 40-77°F/5-25°C. Higher humidity can shorten shelf life.
• Avoid contamination from dirt, debris and other chemicals. Use funnels when refilling the tank.

By following the above storage guidelines, AdBlue fluid purchased from a reputable source should last at least 18 months. Check labels for the manufacturer date.

If the fluid ever appears cloudy, thickened or has visible particles, it means the urea content has broken down. Do not use degraded AdBlue as it can damage SCR components.

Disposing AdBlue Correctly

While AdBlue itself is non-hazardous, it should be disposed responsibly as excess nitrogen can potentially damage ecosystems:

• Avoid pouring it into drains, storm sewers or directly on soil. Check if any auto parts stores accept AdBlue for recycling.
• Neutralize diluted AdBlue by mixing with an ammonia remover chemical before disposal. Running it through a bio-filter also works.
• Evaporate excess liquid AdBlue safely away from plants/animals, rainwater runoff or groundwater access.

AdBlue bottles, funnels and other hardware can be recycled normally as regular plastic waste once thoroughly rinsed.

By taking care to store, handle and dispose of AdBlue prudently, diesel owners can reduce refueling hassles and safely enjoy the benefits of cleaner running SCR-equipped vehicles for years to come.