It’s an ongoing debate: which fuel type provides the lowest total cost of ownership (TCO) to school bus fleets. Opinions abound on all sides of the matter. A gasoline-powered bus has a low initial purchase price, so it must have the lowest TCO. Propane fuel costs much less than clean-diesel, so a propane-powered bus must have the lowest total cost of ownership. And compressed natural gas (CNG) buses have a high initial purchase price, but advocates contend that after the initial cost is recouped, the savings on CNG fuel contribute to a low total cost of ownership.
And scientific studies, like one conducted by the University of Michigan Transportation Research Institute, have shown that clean-diesel has the lowest total cost of ownership, but the study mostly accounted for passenger vehicles. So which is it? Which fuel type costs fleets the least over the total lifecycle of a bus?
Well, the answer, unfortunately, is: it depends. The problem with determining the total cost of ownership for a bus of any fuel type is that in most cases, all factors are not considered. This creates one-sided arguments and speculations. Plus, the costs vary based on usage, terrain, climate, and even factors such as geography and fuel availability.
Luckily, there are some truths that can be universally applied when determining what fuel type offers your school district the lowest total cost of ownership.
As fuel costs ebb and flow, it’s important to remember not to consider fuel costs at face value. In order to get a clear picture of the true cost to fuel a school bus, you must also consider fuel economy and fuel efficiency. The more efficient an engine is, the less fuel it burns and the further it travels on a single gallon of fuel. So even if one type of fuel is less expensive per gallon-equivalent, the efficiency of that engine type may negate the savings.
For example, clean-diesel is the most energy-efficient fuel type, which means that clean-diesel outperforms other fuels in operating range and fuel economy per gallon of fuel. On average a clean-diesel school bus engine provides up to 50 percent better fuel economy than any other similar-sized gasoline, propane or compressed natural gas engine. What this means is that other fuels could technically have to cost 50 percent less than clean-diesel in order to achieve fuel cost savings.
Maintenance cost is another important factor to consider when examining TCO. Each type of school bus engine requires its own maintenance schedule. While clean-diesel engines need DEF fluid and particulate filters, spark-ignited engines, such as gasoline and propane engines, require costly ignition tune-ups.
Plus, newer school bus engines often have extended maintenance intervals that are quite different from older school buses. For example, the new Detroit™ DD5™ clean-diesel engines have the longest service intervals in the industry with up to 45,000-mile oil change intervals and have advanced aftertreatment systems that drastically cut down on aftertreatment maintenance.
On top of ongoing maintenance, you should also consider the cost of complete engine overhauls. While not usually a point of discussion during the buying process, many school districts don’t ask about engine lifecycle and costs associated with engine replacement. Many spark-ignited engines like propane or gasoline may need to be completely replaced one, two or even three times during the total lifecycle of a school bus, while clean-diesel engines last 15 to 20 years or more before requiring replacement.
The bottom line is, for any fuel type, it’s important to research the specific type of maintenance needed, consider replacement intervals and cost, and weigh the cost-benefits.
Alternative Fuel Costs
Switching to an alternative fuel can give fleets a break in capital and fuel costs because many programs are still offering grants and incentives to switch to an alternative fuel. The discounts and incentives vary by state, so it is definitely worth looking into.
On the flip side, consider the costs required to incorporate a new fuel type into your district. In addition to new fueling infrastructure, school bus fleets may also have to invest in maintenance bay upgrades, new maintenance equipment and even driver and technician training based on the fuel choice.
Capital Cost and Resale Values
Last, the capital cost of a school bus is the most prominent aspect of the total cost of ownership equation. Many fleets select the cheapest bus, often gasoline school buses, without weighing the cost of owning that bus down the road, or selling the bus at the end of its lifecycle. In the long run, the lowest initial cost option may not be the most cost-efficient overall.
For instance, there are vast differences in the resale value of school buses. Clean-diesel has the highest resale value in the market today; the large resale market for clean-diesel just doesn’t exist for gasoline, propane or compressed natural gas-powered buses.
Again, it’s important to weigh the pros and cons of a specific fuel type based on your unique needs. And it is just as important to consider every aspect of the total cost of ownership equation to make the best decision. When all factors are considered, clean-diesel has the lowest total cost of ownership for a fleet. But again, a school district’s needs vary based on terrain, geography, etc.
When examining the TCO of your school bus purchases, challenge past assumptions, ask tough questions, and have an open mind. You may be surprised by what you find out.
To learn more about the many benefits of clean-diesel school buses or their total cost of ownership, visit our Facts About Fuels page.