Editing Diesel engine (section)

=== Efficiency ===

The [[fuel efficiency]] of diesel engines is better than most other types of combustion engines,<ref name="Dubbel_1981_712" /><ref name="Reif_2014_10" /> due to their high compression ratio, high [[air-fuel ratio#Air–fuel equivalence ratio (λ)|air–fuel equivalence ratio (λ)]],<ref name="Pischinger Kell Sams p. 137–138">{{Cite book |last1=Pischinger |first1=Rudolf |title=Thermodynamik der Verbrennungskraftmaschine |last2=Kell |first2=Manfred |last3=Sams |first3=Theodor |date=2009 |publisher=Springer-Verlag |isbn=978-3-211-99277-7 |publication-place=Wien |pages=137–138 |language=de |oclc=694772436}}</ref> and the lack of intake air restrictions (i.e. throttle valves). Theoretically, the highest possible efficiency for a diesel engine is 75%.<ref name="Hemmerlein_1991" /> However, in practice the efficiency is much lower, with efficiencies of up to 43% for passenger car engines,<ref name="vB_2017_755" /> up to 45% for large truck and bus engines, and up to 55% for large two-stroke marine engines.<ref name="Reif_2014_13" /><ref name="EPA_2004" /> The average efficiency over a motor vehicle driving cycle is lower than the diesel engine's peak efficiency (for example, a 37% average efficiency for an engine with a peak efficiency of 44%).<ref name="Soimar_2000" /> That is because the fuel efficiency of a diesel engine drops at lower loads, however, it does not drop quite as fast as the Otto (spark ignition) engine's.<ref name="Karle p. 53">{{Cite book |last=Karle |first=Anton |title=Elektromobilität Grundlagen und Praxis; mit 21 Tabellen |date=2015 |isbn=978-3-446-44339-6 |publication-place=München |page=53 |language=de |oclc=898294813}}</ref>