check out ...
formatting link
for example - there is also a useful search engine there. I remember seeing soem photos posted there
Ideally, should be not more than a wisp of white 'steam' - I think the rule is that if it pushes off the loosened cap then it's bad news otherwise forhet about it - engine could just need a good thrash to free up rings for example.
Steve
Any comments on what does it mean if, while the engine is running,with
> the filler cap off, there is some sputtering of oil and smoke coming > out.