What oil viscosity to use on a 99 Audi A4?

I just bought the car, I want to change the oil on it but I don't know what viscosity to use. Someone told me that it didn't matter but it had to be synthetic %26amp; someone else told me that it had to be 20W-50, they didn't say anything about synthetic. I need to change it asap, any help is greatly appreciated, thank you.What oil viscosity to use on a 99 Audi A4?5w30 any oilWhat oil viscosity to use on a 99 Audi A4?I would recommend using Mobil 1 0w-40 full synthetic. There are many sludge problems with VAG's 1.8T I-4 engine, and using this oil is a step to prevent that costly repair. You can use another oil of similar weight, but being an Audi owner myself and knowing how much easier it is to prevent issues than fix them, just make sure it's synthetic and meets VW 502 standards.