Six key things to consider when going alternative

Transitioning all or part of a fleet to alternative fuel vehicles can be an exciting new venture. Alternative fuel engines, such as propane and compressed natural gas (CNG), are definitely staking their claim in the marketplace as their key advantages are being realized.

While fleets enjoy fuel savings and a boost in their image from their environmental efforts, there are other factors to think about. From initial costs to fueling stations, maintenance and safety measures, changing a fleet over to alternative fuel can be a major shift for any fleet – and one that the fleet manager, as well as the maintenance manager and crew, should fully understand.



When switching to alternative fuels, the first thing to consider is initial cost. Investing in an alternative fuel truck or bus will generate significant fuel savings over time. The time it takes to recoup the initial investment may be greatly reduced versus the purchase of a diesel-powered vehicle.

The initial cost of an alternative fuel vehicle can be slightly more, in addition to the costs for fueling stations, maintenance equipment, training and possibly new staff. It is wise to also consider possible government grants and tax breaks in the total cost of ownership savings that the fleet will yield down the road.

Start-up costs differ for each fleet, so the decision to shift to alternative fuel must be made on a case-by-case basis.



For any type of new alternative vehicle, the method of fueling is a consideration.

For CNG engines, the garage will definitely need to install a CNG fueling station to fill the buses or trucks, unless there are fueling stations nearby. CNG fueling stations come in two varieties:

  • Slow-fill, which are designed to fill the vehicle’s tank overnight when not in use and kept at the compound.
  • Fast-fill, which will fill the tank in about the same amount of time as filling a traditional diesel tank.

Each type of fueling station has its own benefits depending on how the fleet is compounded and operated.

The same holds true for propane vehicles. Propane stations can be added to an existing property relatively easily because they are available as skid systems that can be dropped into place on the lot. This setup can be moved easily, if necessary.

The cost for a propane station can be significantly lower than the cost of a CNG station.

Even operators of hybrid/electric vehicles need to plan for fueling. Hybrids typically run on diesel. However, fleets with hybrids that are charged through a plug will require power poles for recharging.

No matter what type of alternative fuel vehicle is selected, fleets should always check local ordinances prior to installing a fueling station.



Most fleets want to know about fuel savings associated with alternative fuels. Technicians, on the other hand, want to know what it takes to maintain alternative fuel vehicles to keep them up and running.


For hybrid engines, technicians must know and understand how the hybrid system works and what safety precautions to keep in mind around high-voltage systems. However, because a hybrid bus or truck runs off a manual transmission that has been automated, there are only minor maintenance requirements aside from changing clutches, air filters and adding coolant.

The hybrid system is a self-contained system that does not require maintenance in and of itself. If the system does signal a fault, the vehicle will switch over to running like a standard diesel vehicle and an error code will be displayed. This error code will then guide the technician to the problem.

Because in-depth repairs require extra software and tools that most fleets do not carry, extended maintenance or repairs on hybrid engines – beyond very basic functions, such as changing clutches, air filters or coolant – are usually performed at the dealer location.


With CNG engines, the maintenance of CNG fuel filters is most important. Because oil is used to compress natural gas, oil may enter some vehicles’ fueling systems. This oil can be trapped in the fuel filter or the low pressure filter. These filters must be inspected and replaced regularly.

Also, filters must be changed more frequently if the fuel source is not clean or older and/or dirty fueling stations are utilized. Not maintaining the engine, including not promptly replacing fuel filters, can greatly impact the safety of the bus or truck and impair the performance of the vehicle.

CNG engines require different engine oil than that used in a standard diesel engine. CNG engines use low-ash natural gas oil, so technicians must exercise caution, ensuring that the correct fluid is used when performing a service on a CNG platform. Using the wrong engine oil can cause severe damage to the engine.

Additionally, technicians must change spark plugs regularly – something that is not a standard practice for diesel engines.

Last, with CNG engines, technicians must be familiar with the National Fire Protection Association Code 52. This code mandates that customers inspect their fuel cylinders at least once every two years for nicks and cuts, plus recommends an annual inspection. An inspection by a certified inspector must take place every three years. After a tank has been in use for 15 to 20 years, it must be replaced.

Thomas Built Buses uses Type 3 and Type 4 fuel cylinders. The Type 3 fuel cylinder is an aluminum cylinder with a nylon fiberglass overwrap. Type 4 is a composite cylinder with a nylon fiberglass overwrap.

The fiberglass overwrap on both of these fuel cylinders helps to reduce the chances of deep cuts or gouges on the fuel cylinders. Annual or biannual inspections from customers or their service crews are imperative.


Propane engines are maintained in the same way as gasoline engines and utilize many of the same components. As with CNG, fuel system filtration is key to getting good performance. The spark plugs also must be changed regularly.



One of the biggest safety concerns with alternative fuels is a fuel leak on a CNG- or propane-powered vehicle. In the event of a leak, each fuel reacts in a different way.

CNG is lighter than air and will float up and away from the vehicle unless trapped in the engine compartment. For that reason, there is vent piping in the vehicle to let the fuel vapor escape the engine compartment.

Propane, on the other hand, is heavier than air and will settle to the ground during a leak.

Compressed natural gas buses by Thomas Built are equipped with several different mitigation features to ensure safe practices. The first of these is a fuel shut-off device. This is an electronic switch at the fuel-fill door that, when opened, turns off the fuel supply to the engine during fueling. When fueling is complete and the fuel door is closed, the fuel shut-off is reopened to allow the bus to operate again.

There are manual shut-off valves as well. All of these safety mechanisms ensure that buses remain off during fueling.

Thomas Built Buses CNG units also have stainless steel fuel lines to greatly decrease the risk of a methane leak. Along with fuel tanks that are mounted safely beneath, a crash barrier and a stone shield also protect the system from impact, stones and gravel.

For hybrid vehicles, Eaton offers training and videos for first responders to review special procedures in the event of an accident involving a hybrid vehicle. The hybrid high-voltage cables are protected with bright orange coverings so they are easily distinguished from the standard vehicle wiring.



When using alternative fuels, some shop improvements must be made as well. Fleets must check with local agencies to see if particular standards are required.

Most areas require a shop ventilation system to be installed in case of a leak. With CNG, the ventilation systems are mounted in the roof, so when a CNG leak is detected, the ventilation system will open vents in the roof or activate fans to exhaust the air.

With propane, the detectors are mounted at ground level or inside of service pits and the ventilation system will evacuate the air from the pit- or low-level area.



Shop heating systems cannot be overlooked. Although this is not something automatically considered when investing in alternative fuels, there are important safety implications.

Many garages today use heaters in their workspace. CNG engines, however, cannot be serviced when there is an open flame, gas or pilot heater in the shop because of a potential leak.

If investing in an alternative fuel engine, fleet managers should be prepared to review their garage’s heating devices to determine if they pose a potential hazard.



All in all, choosing an alternative fuel vehicle has many benefits – including tremendous cost savings. However, before implementing alternative fuels, fleets must be sure to fully understand the training, maintenance and education that may be required to make the new fleet truly successful.


Mike Stotler is the manager of service education at Thomas Built Buses ( Founded in 1916, Thomas Built Buses is one of the country’s leading bus manufacturers and offers a full line of school, childcare, activity, green and specialty buses. It is a subsidiary of Daimler Trucks North America (, the largest heavy duty truck manufacturer in North America and a leading manufacturer of Class 4 to 8 vehicles. Daimler Truck’s other vehicle brands are Freightliner and Western Star.