Diesel still moves the heaviest work in most fleets, and it is not going anywhere. But the cost of running it is no longer just the price at the pump. For fleet managers, the question is no longer diesel or gasoline. It is where each fuel makes sense for the budget, and how to stay flexible when the ground keeps shifting.
Booster supports fleets with a variety of fuel needs. Our Smart Tankers are built to accurately deliver multiple fuel types on the same delivery trips to keep our work as efficient as the fleets we serve. Right now, this ability matters more than ever. Regulatory exposure, compliance risk, and emissions-system downtime have turned diesel’s true cost into a moving target, and a $1.6 billion settlement in the last two years put that reality on the front page.
What is the Hino Settlement & How Has It Changed Diesel Fleet Fueling?
In January 2025, EPA, the Department of Justice, and the California Air Resources Board announced a global settlement valued at more than $1.6 billion with Hino Motors, a Toyota subsidiary, over falsified engine emissions data. The case covered roughly 105,000 model year 2010-2019 heavy-duty highway engines and about 5,700 nonroad engines. In the largest action of its kind, EPA voided the certificates of conformity for those engines.
Importantly, the settlement is narrowly scoped. It applies to specific engine and model-year populations, the associated recall is not mandatory, and new Hino trucks sold today use engines built by other manufacturers. For fleet managers, it is not that one brand is uniquely risky. The ultimate takeaway is that regulatory and compliance costs sit inside diesel ownership in ways an invoice never shows, and these costs can surface years after a vehicle is purchased.
Why Are Emissions Systems Such a Wild Card?
Modern diesel engines rely on layered aftertreatment. This includes diesel particulate filters, selective catalytic reduction, and the diesel exhaust fluid gas that feeds it. When a sensor faults or fluid runs low, the engine can derate into limp mode. For an operation running low-mileage, stop-and-go, or high-idle routes like logistics providers, emergency medical services, and transportation providers, those systems carry a heavier maintenance burden than the vehicle’s core drivetrain, and the downtime that is associated with repair is often a real expense fleets aren’t prepared to absorb. A truck sitting at a dealer for an emissions fault costs a service or delivery fleet far more in missed work than it ever saved in fuel economy.
The regulations that govern alerts and maintenance to these systems are also under review. In 2025, EPA moved to soften the long-standing derate that could slow a faulted truck to a crawl, and in 2026 it proposed replacing DEF-related derates with dashboard alerts for newer engines, all while leaving the underlying emissions standards in place. For fleet managers, these shifting rules are their own planning challenge: The cost of a diesel asset depends partly on regulations that keep changing underneath it.
Does This Mean Fleets Are Dropping Diesel?
No, and framing it that way misses what is actually happening. Fleets are becoming more selective about where diesel makes sense for their company needs. A growing number of 20 to 40 vehicle operations now run a deliberate mix: gasoline step vans and medium-duty trucks for lighter, local, stop-and-go work, with diesel reserved for the heavier-duty units where its torque and range genuinely pay off. In that model, diesel is not a shrinking afterthought. It is the piece that keeps a fleet from needing an entirely separate fueling solution.
That shift makes fuel flexibility more valuable, not less. The fleets best positioned for an unpredictable market are the ones that can lean on whichever fuel makes sense for the route, the regulation, and the price on a given day.
Where Does Renewable Diesel Fit Into Your Evolving Fuel Strategy?
For diesel fleet fueling, flexibility does not stop at gasoline. As we’ve discussed before, renewable diesel is a true drop-in fuel: It runs in existing diesel engines and dispenses from the same tanks and equipment, with no engine modifications or infrastructure changes. That lets a fleet keep the diesel assets it depends on while gaining another lever to pull on cost and emissions exposure. In several West Coast markets, renewable diesel has recently traded at or near price parity with conventional diesel at the pump, which removes the historical premium that kept many fleets from considering it. And renewable diesel sits alongside conventional diesel and biodiesel blends in Booster’s diesel fleet delivery lineup, so adding it to the rotation is a matter of choosing it, not re-engineering anything.
How Mixed Fleet Fueling Supports Teams with Fluctuating Needs
This is where mixed fleet fuel delivery does quiet, compounding work. Booster delivers gasoline, diesel, and renewable diesel, and Booster’s Smart Tankers can carry multiple fuel types in a single trip. This means we can work with your needs even as they evolve.
Building a mixed fleet does not mean adding a second fueling process, a second vendor, or a second set of on-site infrastructure. As a company’s needs change and their vehicle inventory shifts, fleet managers can adjust their gasoline-to-diesel ratio. They can also make vehicle-by-vehicle changes monthly where renewable diesel can be dropped in as a more affordable alternative. Neither of these choices require changes to their fuel vendor or their fueling practice. The complexity of a diversified fleet stays off the fleet manager’s plate.
How Fuel Usage Visibility Enables Better Flexible Fuel Management
Flexibility only helps when it is backed by visibility. Booster reports fuel usage vehicle by vehicle, which is exactly the data a manager needs to decide where diesel is worth its added complexity and where a gasoline unit would do the same job for less. Instead of guessing, fleet leaders can see real per-vehicle economics, track consumption by location or route, and build the fuel mix around evidence rather than instinct.
When regulations and compliance costs keep moving, that clear view is what turns a reactive fleet into a strategic one. Per-vehicle data can inform emissions reporting and compliance. At the same time, diesel is not being sidelined. It is being placed with intent. For fleets navigating a market where the rules and the risks keep shifting, the advantage goes to whoever has the most options – and the clearest view of how each one performs.
To see where a mixed-fuel strategy could save across a specific fleet, reach out to the Booster team to discuss your options.