reviving old thread again.
frustrated a bit coz just confirmed that my honda city L15Z1 engine is leaking from somewhere at the top. I suspect it was because the mechanic overfilled the full 4L into the car during my last service 6 months ago (whole bottle completely emptied).

I did a quick check under the car last saturday and found oil on the bottom engine cover. i went to a trusted mechanic to inspect where the oil is coming from. looks like its coming from the engine oil cap and potentially also the cam cover, and maybe even the flywheel oil seal as well (which costs a bomb to reseal because need to pull out the gearbox).

i checked the dipstick and it was still about 0.5cm over the max indicator hole even with the leak and almost 10k km distance travelled since the last service.

for context my car was purchased May 2014 so it is 10 years old now. so i guess your feedback that if the "engine is in good condition, usually no issue" applies. its likely my seals are already a bit worn due to their age so when the mechanic overfilled completely, the seals couldnt take it and started leaking.

it was close to 50% more than the max line right after filling the EO. i raised a concern to the mechanic and asked him to suck out. he was adamant that it was fine and i shouldnt worry about it.
i work in oil n gas so when I see a max line, I follow the max line because why the heck would there be a MAXIMUM indicator if it is fine to go beyond the max, right? but in this case, im not the expert so I trusted him even though my gut told me I should have insisted he pump out the excess.

but yeah, its true that the seals were probably not in the best condition anyway. but I posted this anyway so that others can learn from this and potential further the longevity of their own seals by simply insisting on following the max indicator.

no, bro. if we are talking about >20 year old engines you might be ok to overfill the EO.
modern engines are designed to tight tolerances and overfilling can cause pressure build-up and damage the seals and gaskets.

there is no easy way to know how much EO is too much so the best policy is to just follow the indicators.