Eating fish and fries cooked in    oil used for other meats etc.
Question

As-Salamu 'alaikum
In many restaurants in the West, food such as fish, potato fries, chicken are fried in large deep fat fryers.
The large fryer contains a large amount of oil.
Is it permissible to eat fish and potato fries which have been cooked in this oil, if non-halaal meat and /or pork has also been fried in it ?
And is it necessary to ask the shopkeeper whether he fries everything in the same oil, or should you not ask and just eat ?
This is a real day to day problem affecting many Muslims living in the West.
Jazakumullaahu khairan.
Praise be to Allah.We put this question to Shaykh Muhammad ibn Saalih al-Uthaymeen, may Allaah preserve him, who replied as follows:
So long as we know that most of the food cooked in it is impure, such as dead meat or pork, then we have to ask, but if we do not know that, then we do not need to ask.
And Allaah knows best.