Straight diesel and gasoline engines are no longer the only way to go for your fleet of trucks. But are they still the smartest answer?

The vast majority of vocational trucks serving the pumping and portable sanitation industry are driven by popular diesel power plants. However, alternative power sources — gasoline, natural gas, propane, hybrid and fully electric — may offer advantages to your operation.

Why should you consider alternative fuels?

  1. Proper specification for your application
  2. Fuel and maintenance savings
  3. Emissions
  4. Promoting a “green” image

When specifying a truck, selection criteria are determined by many factors including annual mileage, terrain, elevation, gross weight, governmental regulation, PTO selection, driver retention, maintenance, fuel availability and marketing goals.

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Starting the process:

The various fuel types do not work well in all applications. An in-depth analysis of your operations — truck by truck, route by route — and a description of the makeup of your fleet is the starting point for considering alternative fuels. Compile data including mileage, PTO hours, fuel costs and maintenance costs per truck. Operational concerns such as terrain, weather and range per day are selection factors. In addition, the company’s goals and objectives are helpful in determining the specification.

Let’s use a hypothetical roster of equipment for a septic service and portable restroom company with 14 diesel-powered trucks:

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Year Model Body GVWR Annual Mileage
2009 Ford F-250 Pickup 9,000 lbs. Class 2 22,847
2010 Ford F-250 Pickup 9,000 lbs. Class 2 27,184
2013 Ford F-350 Pickup 12,000 lbs. Class 3 29,671
2015 Ford F-350 Pickup 12,000 lbs. Class 3 28,377
2008 Ford F-550 Restrooms 19,500 lbs. Class 5 21,983
2010 Ford F-550 Restrooms 19,500 lbs. Class 5 27,841
2005 Freightliner M2 2,500-Gal. Septic 33,000 lbs. Class 7 25,684
2008 Freightliner M2 2,500-Gal. Septic 33,000 lbs. Class 7 28,749
2014 Freightliner M2 2,500-Gal. Septic 33,000 lbs. Class 7 26,518
2015 Western Star 4700 4,000-Gal. Septic 58,000 lbs. Class 8 47,432
2015 Western Star 4700 4,000-Gal. Septic 58,000 lbs. Class 8 50,639
2015 Western Star 4700 4,000-Gal. Septic 58,000 lbs. Class 8 49,276
2005 Ford F-750 Flat Dump 26,000 lbs. Class 6 17,628
2005 Ford F-750 Flat Dump 26,000 lbs. Class 6 18,813

This company operates in northern Georgia. Their office is at 750 feet above sea level, but they service some customers in the mountains with elevations up to 2,500 feet, so terrain is hilly. The F-250, F-350 and F-750 trucks are for septic installation and are on construction sites regularly. The F-350s also tow trailers for portable restroom deliveries to events and construction sites. The restroom route trucks never leave an improved road (some dirt). The small vacuum trucks occasionally will pull into a driveway or backyard and pull a small trackhoe. The Western Stars never leave pavement and also pull a trackhoe.

The company has had maintenance issues with emissions systems on trucks newer than 2007. They are thinking of upgrading their older trucks. The per-hour cost of operation is in the $60 range across the fleet. Georgia is a tandem-only state and does not have any incentives for alternative fuels. Alternative fueling stations are not common in the area of operation.

There are two company goals: reduce costs and to cultivate a “green” image by having an alternatively powered “green” truck. An analysis of this fleet shows some potential for alternative power plants. Let’s look at the options:

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Gasoline has been powering trucks for more than 100 years. It is best suited to low-mileage applications of 25,000 miles or less per year. It is available for Class 7 (33,000 lbs. GVWR) and smaller.

Strengths: The cost of equipment acquisition is substantially lower, fuel is readily available, no special requirements or concerns in handling fuel, simple and reliable catalyst-based emission system, and maintenance facilities are plentiful

Weaknesses: Different power curve requires higher rpm to generate torque, mpg is less, more frequent maintenance intervals, limited PTO applications, and not environmentally friendly

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In applications with 600 hours or 25,000 miles usage annually, gasoline is a viable option. The total cost of ownership will be less due to the reduced cost of acquisition, reduced maintenance costs and reduced downtime issues. Gasoline is the fuel of choice for passenger cars and light trucks.

Natural gas

Natural gas has been powering trucks for approximately 20 years and comes in two forms: compressed (CNG) and liquid (LNG). CNG is compressed to 150 PSI for storage. LNG is refrigerated to 294 degrees below zero for storage. It is available for classes 3-8.

Strengths: Extremely clean burning, fuel costs are low, good power curves, can be government subsidized, and LNG offers good range

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Weakness: Requires specialized maintenance and fueling facilities, CNG has limited range and large fuel tank requirements, and LNG has fuel-handling safety concerns (due to cold) and fuel loss due to evaporation

CNG works well in applications that are predictable (route driven) and an economy of scale can be achieved with enough units. CNG has gained acceptance in the municipal solid waste segment (trash) and in the government segment. LNG works well for over-the-road applications provided fueling is planned and predictable.


Propane has been powering trucks for more than 50 years and is readily available. Propane has characteristics similar to gasoline, but it burns cleaner. It is available for Class 3-7 trucks.

Strengths: Readily available fueling stations, simple and reliable catalyst-based emissions system, maintenance, ultraclean burn, and can have governmental subsidies

Weaknesses: Different power curve requires higher rpm to generate torque, mpg is less, more frequent maintenance intervals, limited PTO applications, and minor fueling issues (pressurized to 60 PSI) and some cold weather issues

Propane works well in applications similar to gasoline and can be considered a gasoline substitute. Acquisition cost is slightly higher but not significantly higher. Propane has the greatest penetration into a distribution market (propane bobtail tank trucks).

Hybrid electric

Hybrid technologies have been used in heavy-haul applications since the 1950s. Options are available in class 3-8 trucks.

Strengths: Powerful and versatile, clean operation, and government subsidies

Weaknesses: Acquisition expense, PTO issues, and tare weight issues

The best example of a heavy-haul hybrid vehicle is a locomotive. The diesel engine powers a generator that provides propulsion to the wheels. There are some examples of this type of propulsion in the trucking industry. has introduced a technology in the refuse industry with some success. The Hino 195h is a production model and other manufactures have introduced limited runs of hybrid powertrains. No great penetration of any market has been gained by hybrid vehicles.


Electricity has been powering a small number of vehicles for more than 75 years.

Strengths: Powerful and versatile, clean operation, simplified maintenance, and governmental subsidies

Weaknesses: Range, acquisition expense, lack of availability, PTO issues, and tare weight issues

While there are currently fully electric passenger cars, there are no viable electric vehicles operating in the commercial market. Many prototypes are in development and being testing. The greatest problem with electric vehicles is energy storage capacity. Current battery technology is not practically viable for fully electric commercial vehicles.


How does this apply to our example company? Reviewing the data provided shows some alternative power plant options.

The vacuum trucks and the pickups are best served by diesel. All run in the higher mileage/hour range and need the power of the diesel to work most effectively. Natural gas would work for these applications, but the acquisition cost and fueling issues detract from that option. Propane is an option for the pickups and the Class 7 vacuum trucks, but the mileage might lead to an increase in fuel costs.

Using the parameters outlined, the F-750s and the portable sanitation trucks could use either gasoline or propane power for alternative fuel sources. Both fuels are easy to handle, readily available and provide good performance. Either alternative achieves the goal of reducing expenses via acquisition cost, maintenance and fuel cost savings. Propane would offer the ability to market a green truck. Company management would need to further study a potential choice.

This article is not designed to give you clear answers, but to offer a guideline to frame your truck power plant options. In a future article, I will discuss the missing alternative fuel: biodiesel.

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