In how many miles do I need to clean the injectors ?

 

I could be wrong, but I don't think you should need to normally if you're using the recommended Top Tier premium petrol. It's got all kinds of detergent additives to keep the injectors clean as you drive.

 

I went to BMW service he said you have to clean you injectors after 30000 miles, I am not sure is that right ?

 

If getting good quality gas is difficult in Turkey, can't sat as I've never been, then I would recommend a good fuel additive. Perhaps twice a month depending on how much driving you do. I have used techtron in the past with good results.