Citroen C5 Engine Oil From Sep 2004 to Feb 2008 Available Here. What engine oil do I need is one of the most common questions we hear at MicksGarage. We can understand why, because choosing the right car engine oil can be confusing. Using the engine oil finder will ensure you get the right spec oil for your car. Bear in mind that more than one grade of oil might be recommended. For example, 5w30 engine oil and 10w40 engine oil might be suitable for your car. The oil finder system also tells you how much oil your car needs and how often you need to change your oil. It really does take all the guesswork away when selecting which engine oil suits your car. Experts recommend you change your oil every 3000 miles. It's possible that you will need to top up your oil in-between services as well. To avoid paying high garage forecourt prices it's a good idea to keep a 1 lite top-up of oil in your boot. When selecting the right oil for your car, don't assume that cheap engine oil will be poor quality. Also don't assume that the most expensive is the best engine oil. Choose the right spec oil for your car and change it regularly. If you still need help, don't hesitate to contact our customer service team!