The responsibility for reducing diesel emissions is moving more toward owners and operators rather than manufacturers. Historically, reducing emissions from diesel engines and machines has been totally an issue between engine makers and EPA regulators, where new clean air standards were set and manufacturers made design changes to meet the standards. Owners and operators simply purchased the new model engines and equipment, and over time, newer engines replace older ones and the overall emissions levels improve as the fleet gets newer. However, this trend is changing.

Since Tier 4 emissions will be near zero, the amount of research and development has increased and is more complex compared to previous Tier transitions. Since diesel engines are known for their durability, many older machines will remain in use for years to come and begin accounting for a larger share of diesel emissions. Some of the oldest engines and machines have 20-40 times the emissions levels of a new Tier 4 engine. As new ozone and particulate matter (PM) standards are adopted over the next few years, state and regional officials will be looking for cost-effective, near-term ways to reduce emissions through requirements or aggressive incentives to accelerate the modernizing and upgrading of existing engines and machines (“aka retrofitting”) to lower emissions levels .

Depending on age and condition, an idling diesel engine can consume one-half to one gallon of fuel per hour. Many job sites save multiple machines operating at various intervals that are left idling when not in use. Unlike retrofit regulations, idle reduction measures virtually always have environmental benefits as well as engine benefits and so there will likely be more efforts to raise the awareness about diesel idling and the economics of shutting off engines when not in use; saving money for owners and reducing emissions in the air.