<div class="htmlview paragraph">Synthesized passenger car engine oils have shown a wide range of performance benefits in automotive gasoline engines. These oils also satisfy the additional demands of small diesel engines used in passenger cars and light-duty vehicles. This includes the severe requirements of turbocharged passenger car diesel engines. Excellent high-temperature deposit control, wear protection and fuel economy are documented for synthetic engine oils in U.S. and European diesel engine dynamometer, chassis rolls and fleet tests operated under severe conditions. Many of the field tests were conducted with greatly extended oil drain intervals, further stressing oil quality. Test results support the outstanding passenger car diesel engine lubrication capability for optimized synthetic engine oil formulations.</div> <div class="htmlview paragraph">The performance advantages of synthetic automotive lubricants in gasoline engines have been well documented (<span class="xref">1</span>, <span class="xref">2</span>, <span class="xref">3</span>, <span class="xref">4</span>, <span class="xref">5</span>, <span class="xref">6</span>, <span class="xref">7</span>, <span class="xref">8</span>)*. These benefits included outstanding engine cleanliness and wear protection, superior cold-starting and fuel economy, excellent high-temperature stability and quality reserve for continued performance and protection under the most severe operating conditions and greatly extended service intervals. These same benefits for synthetic engine oils are also available for the small diesel engines in passenger cars and light-duty trucks.</div> <div class="htmlview paragraph">The passenger car diesel engine, although a small segment of the total vehicle population, has become increasingly important in terms of oil quality, particularly with the introduction of turbocharged models.</div> <div class="htmlview paragraph">*Numbers in parentheses designate references</div> <div class="htmlview paragraph">The engine builder's lubricant performance recommendations for passenger car dieselengines require at least API CC and preferably API CD quality, often in conjunction with API SF (or SE) gasoline performance. In many cases, the engine manufacturers have established even more severe requirements for passenger car diesels, such as the Volkswagen 505.00 specification and European engine builder CCMC provisional PD-1 category^{(<span class="xref">9</span>)}.</div> <div class="htmlview paragraph">The work described in this paper documents the outstanding performance of synthetic engine oils in passenger car diesel engines. The data presented covers two viscosity grades, SAE 5W-30 and SAE 5W-50. Both of these formulations are optimized to take full advantage of the use of synthesized base stocks and to provide the maximum performance benefits in all passenger car engines.</div>