How much gas is used idling? Understanding the impact of idling on fleet operations

For fleet managers, unchecked idling doesn't just waste fuel, it impacts profitability and the environment. According to the US Department of Energy, road vehicles in the U.S. consume over 6 billion gallons of fuel per year due to idling, equating to more than $11 billion in waste.

In this comprehensive guide, we'll break down the mechanics of idle fuel usage so you can understand exactly how much gas is used idling. We’ll also dive into how innovative technology solutions like Samsara can help reduce idling, minimize emissions, and improve operational efficiency. 

What is engine idling?

Engine idling occurs when a vehicle's engine runs while the vehicle remains stationary. With the engine running, the vehicle continues to consume fuel to maintain operation and power auxiliary systems without producing any useful work in terms of vehicle movement. This creates a direct inefficiency where fuel is being burned, emissions are being produced, and operational costs are accumulating—all without any productive output.

From a technical perspective, when an engine idles, it draws fuel into the car’s engine combustion chambers where it mixes with air and ignites at a reduced rate compared to when the vehicle is in motion. The fuel consumption rate during idling varies significantly based on several factors:

• Engine size and type: Larger engines typically consume more fuel during idling. A 6-liter engine will generally use more fuel at idle than a 4-liter engine.

• Fuel type: Diesel engines may consume more fuel during idling compared to gasoline engines, though specific rates vary by vehicle model and engine design.

• Auxiliary systems: When systems like air conditioning, heating, or power take-off (PTO) equipment are running during idle, fuel consumption increases substantially.

• Engine condition: Poorly maintained engines or those with mechanical issues often consume more fuel while idling than well-maintained engines.

Fleet operations typically encounter two types of idling:

• Necessary idling: Situations where the engine must remain running for operational purposes, such as during brief stops, when operating auxiliary equipment, or in extreme weather conditions where climate control is essential for safety.

• Unnecessary idling: When engines run without serving an operational need, such as during extended loading or unloading periods, driver breaks, or while waiting at delivery locations.

Some car idling is unavoidable, but understanding the distinction between necessary and unnecessary idling is crucial for optimizing fleet operations. By identifying patterns of unnecessary idling, fleet managers can implement targeted strategies to reduce waste.

How much does idling cost?

Since engine idling is capable of wasting up to a gallon of gas per hour, these costs can grow quickly across a fleet's operations. To understand the true financial impact of a vehicle’s idling engine, we need to examine several key factors that influence idle fuel consumption rates.

Engine size plays a significant role in determining idle fuel consumption. How much fuel does idling actually burn? Larger engines with poor fuel economy typically consume more fuel during idle periods—a 15-liter diesel engine in a Class 8 truck will burn substantially more fuel at idle than a 6-liter engine in a medium-duty vehicle. This variation means that idle reduction strategies may need to be prioritized differently across mixed fleets.

Idle fuel consumption becomes even more complex when auxiliary systems like air conditioning are engaged. When drivers leave vehicles idling to maintain cabin temperature, the air conditioning system places additional load on the engine, significantly increasing fuel consumption.

Beyond direct fuel costs, excessive idling also accelerates engine wear, potentially leading to:

• More frequent maintenance intervals

• Earlier component failures

• Increased oil consumption

• Reduced vehicle resale value

• Higher total cost of ownership

What are the environmental impacts of engine idling?

Idling also has significant environmental impacts that affect sustainability goals and vehicle performance. 

From an emissions perspective, an idling heavy-duty diesel engine can produce approximately 18–22 pounds of carbon dioxide per hour. For a fleet of 50 vehicles idling unnecessarily for one hour each day, this results in roughly 400,000 pounds of CO2 emissions annually—emissions that could be eliminated with effective idle management.

With environmental regulations growing more complex across states and cities, reducing vehicle idling offers a clear path to compliance. Many states now enforce anti-idling laws with steep fines, reflecting the growing focus from states like California, which has CARB, to reduce air pollution and achieve carbon emissions goals.

Best practices for reducing idle time

Implementing effective strategies to minimize idling requires a strategic approach from everyone across the organization. For fleet managers looking to address idle time, here are a few best practices that you can implement:

1. Educate and engage drivers

Driver behavior is the single most influential factor in idle reduction. Effective driver education programs should:

• Quantify the impact: Educate drivers so they understand that idling unnecessarily can actually consume a significant amount of fuel. Even 15 minutes of unnecessary idling per day can waste over 50 gallons of gasoline annually per vehicle.

• Dispel common myths: Address common myths, such as the belief that restarting a vehicle uses more fuel than idling. This is untrue since modern engines typically use less fuel if turned off for more than 30 seconds. Another misconception is that engines need long warm-up times, when most manufacturers recommend just 30 seconds.

• Provide clear guidelines: Establish specific rules for when to keep the car engine off, such as during loading or unloading, waiting periods, or driver breaks.

• Create accountability: Share idling data with drivers regularly, recognizing improvement and addressing issues through driver coaching.

2. Leverage data insights to measure engine idling

Successful idle reduction programs need to have accurate data and ongoing performance tracking. To effectively measure engine idling, you should:

• Establish baselines: Before implementing changes, collect comprehensive data on current idling waste patterns to establish meaningful benchmarks.

• Set specific targets: Define realistic but challenging goals for idle reduction. For example, you can establish a goal that seeks to reduce average daily idle time by 30% within six months.

• Implement regular reporting: Create standardized reports that track idle time by driver, vehicle, and location to identify patterns and opportunities.

• Recognize success: Celebrate achievements and recognize drivers who demonstrate exceptional improvement in reducing unnecessary idling.

3. Use a fleet management solution to improve fuel efficiency

Fleet management solutions with fleet fuel management capabilities like Samsara provide the data and tools needed for fleet managers to make informed, actionable decisions to manage and reduce idle time effectively. Some functionality a fleet management solution can offer includes:

• Real-time idle tracking: Track where, when, and for how long each vehicle is idling to pinpoint problem areas and patterns across the fleet.

• Fuel consumption insights: Monitor the amount of fuel used during idling events to quantify the impact of idling reduction efforts.

• Driver-specific idling data: Use individual driver data to identify excessive idling behaviors and enable targeted coaching that improves fuel efficiency.

• Automated excessive idling alerts: Set up customizable alerts that notify drivers and fleet managers when vehicles idle beyond a set threshold.

• Historical benchmarking: Leverage historical data to benchmark idle performance and set realistic, achievable reduction goals over time.

• Route optimization: Reduce idling by avoiding congested routes and traffic through more efficient routing and dispatch operations.

How Samsara helps fleets reduce idling

Today, modern organizations are leveraging innovative fleet management technology like Samsara to reduce idling, minimize emissions, improve fuel efficiency, and achieve sustainability goals. Samsara leverages AI technology to provide real-time alerts and insights into driver behavior, which can reduce idling by proactively coaching drivers on best practices to minimize fuel consumption and improve regulatory compliance.

For example, Mohawk industries, the largest flooring manufacturer in the world, leveraged Samsara to optimize routing and reduce idling. Prior to Samsara, Mohawk looked to reduce idling but didn’t have visibility into fuel data. With Samsara, they uncovered that many drivers were idling unnecessarily during pre-trip inspections. 

To address this, they took a two-pronged approach—first, they geofenced their locations and set time thresholds to alert managers of out-of-policy idling. Second, and more importantly, they brought drivers into the conversation, asking them to look for opportunities to turn the truck off—this buy-in led to fast results, including a 12% idling reduction and $600,000 in fuel savings. They also gamify fuel efficiency to promote friendly competition among drivers, awarding those with the lowest idle times. 

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To learn more about how Samsara can help you reduce idling, explore Samsara’s Platform solution and speak to our team today.