The simple answer is the max the oil level should be is the max level on the dipstick, that what it is there for. Whilst I accept that a few milimeters will do no damage its a bone idle mechanic who cannot fill the engine to the correct level.

But are you checking the oil correctly? Different makes have different methods. On some its a cold engine after an overnight wait, on others it a hot engine after standing 5 or 10 minutes. The difference can be quite noticable.

But if its been checked correctly and its overfilled get them to drain some.

1. In your opinion, how many millimetres (mm) above the maximum mark on the dipstick of a Ford Focus 1.6 ti vct (petrol) engine would the engine oil have to be to cause frothing of the oil by the spinning crankshaft and also a noticeable affect on engine performance especially on hills? How many millilitres (ml) of oil over would it be? 2. I . Can any mechanics answer please?

No idea, but why don't you try and see by adding 500mls at a time until you see foam, or until you hear a funny noise or smell a funny smell. the report back. All research is informative, and occasionally helpful. Here's a helpful link.

cyrilhuzeblog.com/2012/05/10/engine-oil-question-i.../