It's a good question, @J.R.
My use of the word "cheeky" in the above phrase was used to acknowledge the fact that there is no scheduled oil change immediately after the running in period, so changing the oil at that time would be superfluous to the manufacturer's recommended service intervals.
Furthermore, using "cheeky" was intended to add my characteristic playfulness to my posts, as well as not place any burden of requirement on Lux, who might not have any spare money for what could be argued is a spurious oil change shortly after purchasing a new car.
Beyond that, there is also a subtle cultural implication of pleasure in my use of "cheeky" as it brings to mind (thought possibly not to your mind), the idea of something that can be done fairly quickly and will provide a measure of pleasure.
Hence the rather tired expression "Fancy a cheeky Nando's?", from which I drew inspiration, though one might also have heard "Fancy a cheeky pint at lunchtime?" between colleagues at work.
The lame superfluous filler word I was substituting for "cheeky" would be "quick", which I suggest is the word from which the colloquial use of "cheeky" has evolved, though I'd be willing to hear other people's opinions on its etymology.
Use of the word "quick" would have implied that no other work beyond the oil and filter would be carried out, but while for some the act of changing the oil in their car is a quick job, for others, it is not, and requires some inconvenience.
By substituting "cheeky" for "quick", I acknowledge that the oil change might be unnecessary and possibly inconvenient, but that Lux would be happy with the outcome, without placing any burden of expectation upon Lux that he should change the oil after running in his car.
You grumpy old so and so! 😋