Sales of trucks powered by natural gas are sputtering and growth will be far weaker this year than last as tumbling diesel prices prevent drivers from switching over to the cleaner-burning fuel even though it is cheaper than it has been in years. Sales of medium and heavy duty natural gas trucks are expected to rise less than 1 percent this year after climbing nearly 27 percent in 2014, Power Systems Research, a St. Paul, Minnesota firm that studies engines, told Reuters. It cut that projection from about 4 percent earlier this year. Lured by lower fuel prices and the desire to please increasingly emissions-conscious customers, the trucking industry in recent years has been adopting natural gas as a fuel source despite far higher costs for the trucks. But now oil’s […]