I have an 1.9 CDTI and I want to change the oil, by myself, using what I have found in the how2 section written by Duncan. The question I'm about to ask it's related to the oil : what type I need to use ? I know my car use 5W-20 Super Synthetic Oil as I found 2 stickers above the engine from previous revisions (the car was brought from Germany), and I also found in the manual that I can use another 2 types of oil : 5W-30 and 5W-40.
What is the recommended oil type ?
Another question is related to what I have found also in the manual : with the above oil types, an oil change can be done on a petrol engine after 20,000 miles (30,000 km) and on a diesel engine after 30,000 miles (50,000 km). My last oil change has been made when the car had 103,000 km, and now it has 120,000 km. Is it necessary to change the oil or should I stick to the manual ?
PS. I know this questions may look stupid, but I am really a newbie related to cars, I like my car and I want to learn to take care of it by myself, so please don't be to hard on me.