Our neighbour parks his dilapidated van outside our house which to be honest is fine as he doesn’t get home til we shut the curtains and is gone by the time we get up so he is absolutely entitled to park there and that is fine. However his vehicle has a big oil leak and where he parks mostly on the pavement it’s starting to look really oil stained. Would I be out of order to mention it? For clarity he doesn’t use their driveway which is always empty so he could park it there.