Editing Jaguar XK engine (section)

===Power rating===
During the 1950s and 1960s Jaguar released [[Horsepower#SAE gross power|SAE gross horsepower]] figures, using the measurement system preferred by US manufacturers, as otherwise its cars would have appeared under-powered in comparison with US cars. This practice was superseded by reliance on the more realistic [[Horsepower#SAE net power|SAE net horsepower]] system around 1972, although Jaguar power ratings of that era may also be expressed using the very similar [[Horsepower#Deutsches Institut für Normung 70020 (DIN 70020)|DIN net]] rating system.  Since the conditions upon which the SAE gross figures were determined were not recorded, an objective comparison of the power outputs of the various models of XK powered Jaguar over time is impossible.

The 1965 4.2 XK fitted to the carburetted [[Jaguar E-Type|E-Type]] had a listed output of {{convert|265|hp|kW|0|abbr=on}} SAE gross; the 1986 fuel injected 4.2 XK fitted to the series 3 [[Jaguar XJ6|XJ6]] was listed at {{convert|202|hp|kW|0|abbr=on}} DIN net.{{citation needed|date=June 2018}}  Variables such as compression ratio, cam lifts and durations, and fuel consumption rate for each engine during testing would, at a minimum, be additionally required to develop any estimated comparisons.