I have a Ford Fiesta on a UK P reg (1997 model). I was recently running low
on engine oil and so decided to fill it up. Nonetheless, like a plonker, I
poured 5 litres into the engine (which now seems a bit excessive!) Since
then, when I start my car after leaving it for 12 hours or so, lots of grey
fumes pour out of my exhaust for about 10 seconds or so and then its fine.
If i use my car and then leave it for an hour and then use it again, its
fine with no fumes.