I only experienced liqui moly once with my old wira (very good condition at that point of time)

that is around 2012....
Liqui Moly Engine Flush + Mos2 Leichtlauf 10W40 + Ceratec
(change plug at same time)
End result is impressive, noticeably quieter at idling, till i look twice at RPM meter to confirm engine is running

(and then pop the hood to hear / verify / enjoy the improved sound and smoothness

really naive act i admit that)
I guess it works wonder for old engine with sludge build-up and what not.
But i only tried it once, because the total cost for oil change is pretty expensive, material alone already RM3XX~4XX, exclude oil filter/plug/labour etc
Sadly i sell that good old wira on that same year, still miss it today, as if first girl friend:P
I am also use Mos2 Leichtlauf 10W40 before, that was with my old Suzuki. It was very good. That is why I am asking now whether our Honda City can use or not? haha