The ruling on promotional offers that give the customer a gift if he purchases a specific number of goods

Question : The questioner says: I opened a shop, and in order to attract customers, I made an advertisement. It is that if a customer changes his oil with me five times, the one after that is at half price, and after ten times, the next one is free. This is ten. This is one. Is the question finished?

Answer : It is finished. There is no harm in this, provided that the owner of the shop did not raise the price. If the questioner raised the price, it is not permissible, because if the questioner raises the price, it becomes gambling (maysir), since he may win or he may not win. However, if the price is normal, there is no harm in a person changing his oil with him, and after five times it is at half price, and after ten times it is free.