Issue link: http://read.dmtmag.com/i/71813
Ready for prime time? Freightliner announced that its Cascadia 113-inch BBC daycab soon will be available with natural gas technology using the Cummins ISX 12 G engine. Maintenance changes Most of today's natural gas engines are based on proven diesel designs. For example, there is more than 80 percent parts commonality between the Cummins ISL diesel engine and the Cummins-Westport natural gas engine, says Jeff Campbell of Cummins-Westport. When it comes to maintenance, Today there are 7,500 medium-duty natural gas vehicles and 22,000 heavy-duty designs, such as buses and trash trucks. Freightliner. These upcharges are not likely to go down eventually, as they are a result of higher-priced components like highly specialized fuel systems and tanks that will not cost much less even if economies of scale come into play. Despite its limitations of power density and range compared with diesel, natural gas appears to be working for those willing to accept those tradeoffs in return for lower fuel prices and the noble goals of running a greener operation and taking a small step to wean the United States off foreign oil. "You have to run a lot of miles with the trucks if you're going to make this investment pay off," says Phil Crofts, director of marketing for Burr Ridge, Ill.-based Dillon Transport, which is testing a Peterbilt with a 12-liter LNG engine. "At first, we were unfamiliar with the new engine, the electronics and things like that," Crofts says. "But the fuel is performing almost as advertised." Crofts says the truck isn't getting 46 OVERDRIVE JULY 2012 the utilization Dillon had hoped. "What we've learned is that if you're only going to run 100,000 miles a year, natural gas is probably not going to pay off," he says. "We run our trucks 250,000 to 300,000 miles in a year, and we're saving some sizable chunks of money with those mileage figures. But a lot of that goes out in increased maintenance and in other areas – spark plugs, oil changes and things like that." Compressed natural gas (CNG) and liquefied natural gas (LNG) behave the same once in the combustion chamber, but the manners in which they are delivered, stored, packaged on a vehicle and transported to the combustion chamber are radically different. "Generally speaking, fleets operating on longer routes should ensure they are running on a defined natural gas corridor," says Steve Weiner, alternative fuels marketing manager for Peterbilt. "If the routes are stable, then you can put fuel where you need it. If the routes change frequently, then it can be challenging to ensure fuel availability." There's a simple rule of thumb when looking to convert from diesel to CNG or LNG, says Nadine Haupt, director of alternative fuels for Navistar. For LNG, about twice as much fuel is needed compared to diesel. CNG requires about four here are three of the biggest differences between diesel and natural gas engines: SPARK PLUGS. For technicians, the reintroduction of spark plugs to an industry that moved largely to diesel decades ago is the most noteworthy change. Plugs will need to be replaced every 45,000 miles or so. DEPOSITS AND OIL. Because natural gas engines run significantly hotter than diesel engines, they vaporize oil and create ash. This can form deposits in the combustion chamber and disrupt firing patterns. "A specialized motor oil with lower ash levels that can perform in these higher operating temperatures is a must," says Jim Gambill, Chevron's Delo brand manager, Americas. DRAIN INTERVALS. Oil change intervals are shorter for natural gas engines — another consequence of higher temperatures. In harsh applications, drain intervals as low as every 7,500 miles might be needed. Intervals could extend to 15,000 miles in light-duty applications. times as much as diesel. On smaller routes, CNG is usually more practical because the tank packaging and weight considerations on the chassis are more doable. But for long haul or regional haul, LNG often works, depending on weight and packaging, Haupt says. "Then you have to take a look at what's available in terms of infrastructure," she says. CNG fuel systems store gas in