1. Introduction

This report responds to a request from Senator Jeff Sessions for an analysis of light-duty diesel vehicles, including an examination of relevant technical, economic, regulatory, and environmental issues that could have impacts on market acceptance.¹⁰ The report provides an analysis and assessment of the issues and reports the findings in three chapters that address the topical areas of interest.

GHG reductions could be achieved through increased sales of conventional diesel vehicles as compared to conventional gasoline vehicles; however, competing technologies and alternative fuels could provide equivalent or greater reductions. Currently, as options to reduce petroleum demand and GHG emissions, hybrid and flex-fuel vehicles compete with diesel vehicles as alternatives to conventional gasoline vehicles. Projections of direct well-to-wheels GHG emissions and associated GHG reductions for different vehicle types are presented and discussed in Chapter 2.

Diesel engines are inherently more fuel-efficient than gasoline engines due to attributes associated with the combustion process and the properties of diesel fuel. Diesel vehicles produced and sold today are technically superior to those produced 20 years ago, but lingering consumer perceptions associated with the older diesels have kept sales at a minimum. This, coupled with the cost of emission control equipment required to meet new tailpipe emission standards, has created marketing issues for manufacturers and limited product offerings. In contrast, Western European countries have enacted tax polices that support light-duty diesel vehicles and have proven successful. These issues are examined in detail in Chapter 3.

Prices for highway diesel fuel in the United States currently reflect a cost premium due to imbalances between supply and demand in global markets. The refining industry’s ability to adjust output to keep pace with demand, as well as the continued growth in global demand, will determine how long these price premiums will persist. Issues related to world refining capacity, petroleum fuel demand, and refining technologies are discussed in Chapter 4.

Notes