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The diesel engines built this year are more efficient as the second step of greenhouse-gas Phase 1 standards takes effect. These power plants also offer improved reliability, advanced engineering, reduced maintenance and performance improvements that fleet managers and truck drivers will notice, industry experts said.

To slow the speed of the engine at cruise — called downspeeding, in which every 100 rpm slowed equates to 1% fuel savings — axle ratios are getting numerically lower. To wring the most miles from a gallon of fuel, some fleets are increasingly spec’ing direct-drive instead of overdrive transmissions, which is driving the trend to lower numerical final drive ratios.

WASHINGTON — Shell Rotella has unveiled its new lineup of lubricating oils, products designed to maintain the hotter-burning diesel engines coming in January 2017 and beyond.

Engine makers are providing customers a gauge to help them determine how dependable and durable an engine is supposed to be, called a B-life rating. It’s regarded as the industry standard for measuring the life expectancy of an engine, but the figures are sometimes misunderstood.

Tightening federal standards for truck emissions, including particulates, nitrogen oxides and, most recently, carbon dioxide, have led to higher-pressure fuel-injection systems that require finer fuel filtration than ever before to prevent engine problems.