Halley explained that the move to alternative fuels was initiated after we listened to our customers as their awareness was heightened with regard to the emissions that vehicles produce and their impact on the environment. This awareness helped to shape our strategy as we adapt to the needs of our business. The decision led to a thorough examination of STIs maintenance activities, including its engine oils.

Embracing Propane

There are challenges to keeping a large and varied fleet running efficiently and cost-effectively, Halley said. One key to success is educating its customers about the best ways to move to a zero-emissions strategy.

Through education and straightforward conversation, you can help your customers understand what will truly work for their particular situation and the benefits that can be attained through a structured and stepped approach that reduces emissions in a cost-effective and sustainable manner, he said. To do this, you must have an educated sales team with well-developed and focused technical resources that are available before, during and after presentations to the customer.

Most people do not know what it takes to make an alternative fuel fleet effective, Halley feels. Acquisition, maintenance and administrative operations are all impacted when a company undertakes an alternative fuel program. He added that meaningful gains can only be made when you surround yourself with competent business partners who understand what you want, and are able to deliver the services and products you need to reach your goals of customer service and profitability.

To this end, Student Transportation has formed partnerships with schoolbus builder Bluebird Bus; Roush CleanTech, which upfits their fuel systems to run on propane autogas; and propane providers such as Ferrell Gas and Sapp Brothers to help them meet the needs of their customers. In addition, Halley said, you must have the support of everyone in your organization, up to the highest levels. Communicating this vision – both upstream and downstream – is the key to a successful program.

A primary reason for our success is STI CEO Denis Gallagher, Halley said. His vision of a state-of-the-art, environmentally safe fleet that creates longer-term savings by lowering fuel and operating costs to improve our corporate results is the driving force behind our alternative fuel program.

Follow Through!

Equally important is following through on all aspects of the plan, including capital investment in equipment and facilities, training the workforce, and administrative controls and functions. You cannot short any of these and have an effective implementation of alternative fuels. Trying to take shortcuts does not work, Halley insisted.

Propane is the third most widely used motor fuel in the U.S., and the infrastructure is in place to support it, he continued. The Department of Energy has put out all the cost/benefit analyses you need – from the cost curves to the past history of the costs involved.

According to the Energy Departments alternative fuels website (www.afdc.energy.gov), some 2,500 propane fueling stations now dot the lower 48 states. It says propane typically costs less than gasoline in fleet applications and offers a comparable driving range to conventional fuel. Although it has a higher octane rating than gasoline and potentially more horsepower, it has a lower Btu rating than gasoline or diesel, which results in lower fuel economy.

The DoE also notes that low maintenance costs are one reason behind propanes popularity. The departments website states, The fuels high octane and low-carbon and oil-contamination characteristics have resulted in longer engine life than conventional gasoline engines. Because the fuels mixture of propane and air is completely gaseous, cold-start problems associated with liquid fuel are reduced.

Young, Varied Fleet

STI has grown through both acquisition and expansion. As a result, Halley said, We have quite a varied fleet, with powerplants from International Harvester, Cummins, Mercedes-Benz, Caterpillar and General Motors. This variety also means maintenance personnel must keep track of a variety of engine oil and transmission fluid specifications.

We probably have the youngest fleet in the industry, so we have a good handle on the various technologies in the marketplace, Halley remarked. The average age of our fleet is under seven years.

STI added more than 550 alternative fueled vehicles to its fleet in 2013, bringing the total of such vehicles to nearly 1,000, or 10 percent of the fleet. We received contracts for two public school districts in the Omaha, Neb., area, he said. Between the two, we added 535 buses, of which 435 will be fueled by propane. These buses are powered by 6.8-liter, three-valve V-10 Ford engines, which are factory-prepped to burn propane.

Beside propane, STI also operates buses fueled by compressed natural gas in California. Those are a bit more of a challenge with regard to infrastructure, cost and serviceability, Halley observed.

He again emphasized the need for education – of drivers, service personnel and, most importantly, customers. In the presentation we made in Omaha, we proposed a fleet running on alternative fuels to help lower greenhouse gas emissions. These buses use the latest technology and are some of the cleanest-burning and most fuel-efficient vehicles on the market.

Oil Challenges

Running on propane greatly reduces the carbon and particulate matter in the engine oil. Also, fuel dilution is lower. Propane is injected as a liquid and immediately atomizes into a gas, so you dont have the liquid fuel dilution that you have with diesel. In addition, the engine oil stays very clean. The engines dont have the blow-by and other modes of oil contamination that you have in a diesel engine, Halley noted. The largest contaminant is water that condenses into the oil because of the frequent heat up and cool down cycles on the engine.

Halley added, The clearances in the engine are a little tighter. With SAE 5W-20 oil, youre starting with a little less viscosity, and any dilution would manifest itself more quickly.

Another source of lubricant stress is the smaller sump size – just seven quarts of oil, versus the 16 quarts a conventionally fueled bus or truck might need. If you run a little low on oil, you put a lot of stress on the oil and the engine, Halley explained. On the plus side, propane will ignite at temperatures as low as minus 40 degrees F, so cold start is rarely a problem.

On the negative side, propane does not provide the lubricity of diesel fuel, so Ford hardened the valve seats on its factory-prepped engines to compensate. As a result, the 6.8-liter, V-10 engine has a very long life, Halley noted.

The engines use SAE 5W-20 oil, and Ford specifies an oil change interval of 5,000 miles. We consider the application to be severe duty because it involves frequent starts and stops and intercity driving at relatively slow speeds, Halley said. This places a heavy stress on the engine oil; frequent checks of oil level are critical.

We dont run a lot of miles per vehicle, so we dont do oil analysis, he said. We base our oil changes on mileage. When youre changing only seven quarts of oil versus 16 to 30 in an over-the-road truck, the cost for oil drops significantly, and things like TBN, etc. are not that important.

Despite the higher oil stress, STI is in discussions with Ford about extending the oil drain interval because propane does not load a lot of contaminants into the oil. However, we are probably depleting the additive package quicker; so were considering switching to a full synthetic or a higher quality oil, Halley said. However, its not easy to figure out the tradeoffs between using more expensive oil and extending oil drain interval versus staying with the specified oil and drain interval.