J.D. Power and Associates has awarded Caterpillar's C-15 diesel engine its highest levels of customer satisfaction, marking the fourth consecutive year a Cat on-highway engine won the honor. The C-15 engine won the award in the vocational category, which includes construction, refuse hauling, and utility trucks. "Caterpillar is a perennial strong performer that continues to lead the rest of the industry by a large margin," the marketing firm said.The study was based on interviews with nearly 2,700 customers who own two-year old Class 8 trucks, and measures customer satisfaction in three areas of engine performance: engine quality and warranty; engine performance; and engine noise and vibration.