An ACEA agreement is an agreement between car manufactures and oil producers. ACEA stands for the European Automobile Manufacturers Association, which is an organization that represents the European car industry. The ACEA agreement sets standards for the quality of motor oil and how it should be used in cars. By following these standards, car manufacturers know that the oil they use will be good for their engines, and oil producers can make sure that the oil they make is good enough for cars. This agreement helps make sure that everyone involved in the car industry is using the best products available.