What type of gas for the 2000 BMW?

As you failed to list which model 2000 BMW, I cannot provide an answer. BMW makes many vehicles including diesels. All I can tell you is to use exactly what the owner's manual states. if it states Premium, then use Premium. Using Regular can cause engine damage over time. If it says use Regular, then use Regular. The use of Premium is a waste of money and provides no benefit whatsoever. Of course it it is a Diesel, then use the correct Diesel.