Is it true that the warranty is inapplicable if the vehicle manufacturer’s recommendations have not been followed?

No, the vehicle manufacturer cannot void its warranty if the lubricants and other functional fluids used meet the vehicle manufacturer’s quality and technical performance criteria. The European Commission will not hesitate to initiate proceedings if a vehicle manufacturer threatens not to honor its warranty because of the use of a product of equivalent quality.

Source: UEIL Brochure 2011