Evidently yes, to the extent that {X} includes subjective properties that go beyond the fundamental function of {X}.

To use file formats as an example, the fundamental function of an archive file format is to bundle a set of otherwise-independent files together. A basic archive file format that simply concatenates file contents together (and I guess the necessary header to identify the boundaries between them) wouldn’t be copyrightable. But a more advanced format that includes an index of included files might be, since the addition of the index is a product of some artistry by someone who thought it would be a helpful convenience for users. [1]

Extended to the car example, “putting gas in tank” wouldn’t be copyrightable because no tank can function without gas. But improvements to the method of transferring that gas might be. Engaging a clutch is fundamental to the operation of a transmission and not copyrightable, but a clutch that is specially-designed to require less force might be.

The key is an interesting case though... I suppose I’d have to say that mechanism would have been copyrightable, since one could start an engine in ways other than a key (maybe a crank or a push button), or perhaps because the idea to couple the unlocking mechanism to the engine start signal was a clever idea rather than a fundamental necessity.

[1]: To my understanding, this is exactly the situation with “tar” and “zip,” though fortunately for us the “zip” format was contributed to the public domain rather than copyrighted.