Dealers make the most of their money through aftersales (parts and servicing). We (I work for a main dealer) welcome people bringing in the cars for warranty and service work which they bought elsewhere. The only difficulty comes when something isn’t covered by the manufacturers warranty – if the car was bought from us we would normally do this goodwill, if we could.
Manufactures differ in the way they work, some help the dealer help the customer more than others.
If it was something small, we may do the same for someone who didn’t buy from us, if we thought they would bring there car back for servicing.
We do have some customers who just bring their cars in for warranty work (free to them stuff) and take their cars to intendants for servicing, which is fine, but they are less likely to get things done for them “goodwill”. If the work isn’t covered by warranty.