Why propane is a great choice for a school bus fleet.
School Bus engines are available in many sizes and choices. Diesel has ruled the school bus division for many years, but now alternative fuels are entering the market and producing good results. Funding is also available from the EPA allocated to incentivize a switch from diesel school buses.
Buses operating on propane are environmentally friendly and reliable in cold weather conditions. Propane offers outstanding performance with reduced maintenance cost, efficient reliability, and far less limitations. They start easy in all temperatures, reduce carbon emissions, and emit far less smog producing hydrocarbons and particulate emissions than diesel. Engines warm up quicker allowing heat into the vehicle. They are also much quieter to the relief of drivers, students and community neighborhoods.
In 2017, our district fleet of 62 vehicle started a switch to propane with a purchase of (7) full size school buses. The vehicles were scheduled to be used almost exclusively inside a township with an urban suburban mix. After (3) years and over 100,000 miles, we analyzed our information and developed the following observations.
Fuel Station
One of the first decisions involved with a move to propane will include how the fleet will be fueled. There are many choices for propane suppliers and the different services they offer. An advantage with propane is the ability to sometimes have a propane fueling station installed at your location at little to no additional cost. A reputational propane distributor may install a complete fuel system. The disadvantage is that you are locked into buying fuel from them for a contracted number of years. Some organizations decide to purchase the fuel station outright which gives them the opportunity to check with different vendors for the best possible fuel price.
Another available solution during a power loss, construction issue, or other circumstance is to have the propane company come in at night and have the entire fleet fueled from a tank truck. This is called “bobtail fueling”
Report – Results – Review
ROUSH clean Tech fuel system
Ford 6.8 V-10 Engine (362 HP)
100 Gallon fuel tank
6R140 Ford Built transmission
Improvements we are currently experiencing and future expectations.
Lower Maintenance Costs: Conclusions suggest that maximum impact will be at the maintenance side of operations. Lower maintenance requirements and more up time on the routes are two of the primary reasons propane provides the lowest cost of ownership in the lifespan of a school bus application. Propane produces fewer emissions which have proven to reduce wear and tear on an engine and its fuel system technology. Maintenance intervals on propane buses can be extended which provides immediate savings on oil and filter changes. This perpetual maintenance cost adds up quickly with a large school bus fleet.
Immediate Advantage: The Cummins diesel engines require 17 quarts of oil, the Ford propane vehicle requires only 7 quarts.
Road Service Calls: A stop and go school bus application is difficult with technology necessary on a diesel engine of today. A diesel by its nature wants to run. Clean diesel is a perfect solution in the majority of the transportation needs, but with a school bus, the engine runs but doesn’t get opportunity to reach operating range. Without getting hot enough to burn off emissions they start to build up. The solution is:
Regen: If you are a school bus driver, mechanic, parent, teacher, aide, or police officer, you might know or heard about an engine regeneration. It’s where the school bus stops running with little to no notice. Sometimes there is a blinking yellow light. Often it goes right to red which means to get off the road as soon as possible. A call into the office would have transportation staff discussing driver concerns to mechanics. Regen was most often involved in the conversations. Without burning off emissions, they would build up over time, which in turn would begin to choke the engine. A on the road solution is to flip a switch and put the engine into high idle for an extended period of time, which might be close to an hour. Another solution necessary at times was having to dispatch maintenance staff to the location with laptop information. Whatever the solution or outcome, it involves numerous phone calls, texts, and messages to concerned parents. The dispatch of a technician could also result in lost service time, overtime, and loss of scheduled maintenance repairs.
Down time: A propane fleet avoids the vehicle down time and associated labor costs caused by the continuous maintenance and removal from service necessary to clean diesel particulate filters.
Emissions: Unlike diesel technology, propane does not require a complex emissions system, additional filters, or fluids to comply with EPA clean air standards
Environmentally friendly: Propane has the lowest flammability range of all alternative fuels (2.4– 9.5 percent). Compared to “clean” diesel buses, propane buses reduce nitrogen oxide (NOx) emissions by 96 %.
Kid friendly: The shorter height of younger students puts them face to face with a black cloud of harmful emissions that can aggravate asthma and cause other health issues.
Cold Starts: When the temperatures drop during winter months diesel fuel tends to freeze which leads to clogged fuel filters, lines and often an out of service bus. Preventative measures such as fuel additives or anti-gel agents can help but with an extended cold snap can dramatically increase maintenance costs. Propane requires no fuel additives and delivers reliable starting in any temperature and takes significantly less time to warm up.
Propane disadvantages:
Initial purchase price may be higher: Costs will be offset by reduced maintenance costs. In addition to EPA Clean School Bus funding, many states offer incentives to help fleets save on the upfront purchases of propane.
Fuel Mileage: Propane’s lower British thermal unit rating per gallon results in lower fuel economy, but its lower per-gallon cost can quickly offset the lower fuel economy.
Limited Field Trip Range: Our average across the propane fleet was 5.7 MPG while the same size diesel bus was 7.3 MPG. Because of the properties of propane a fuel tank may be water rated for a certain amount but the total volume might / could be reduced by 80%. A solution for our fleet was to specify a 100 gallon fuel tank. We found it to hold about 93 gallon.
After three years and 100,000 miles of daily operation, the switch to a propane fueled school bus fleet should continue. Except for scheduled maintenance inspections, bus performance has been exceptional. Especially when compared with the same type vehicle equipped with a diesel engine. Driver feedback has been positive, buses are quiet, start easy in cold weather, and heat quickly.
