One source states that the Essex is instead a reverse engineered Buick V6 engine. Toward the end of the 1970s, Ford needed a new six-cylinder engine that was powerful and compact enough to be used in a mid-size car while meeting increasingly stricter emissions and fuel efficiency standards. Since Ford did not have an engine available that could be readily made to meet these requirements, one needed to be developed. The quickest and least expensive approach in accomplishing this was to copy an existing engine from a competitor, which ended up being the Buick V6 from General Motors. Ford's resulting V6 was very similar to that of the original Buick engine — down to an unusual external oil pump design that was common in Buick engines and without precedent in modern Fords — and had a nearly identical displacement. In fact, one of the only major differences between the two engines early on was Ford's use of aluminum heads as opposed to the cast-iron ones used in the original Buick design. However, in the years since the Essex V6's debut, design revisions from both Ford and GM to their respective V6 designs have differentiated their engines from each other to a point that any relationship between the two designs is not as obvious as it once was.