best oil for 2.5L tbi ?

Quality 10W30.

Synthetic is not necessary.

DS

First, replace the valve cover gasket or RTV sealant, whichever it has.

I don't know if 5W-30 was recommended back in 1990 or not. Check your owner's manual and use whatever it recommends. I'd have thought it would be 10W-30, but it may be 5W, I just don't know.

If you don't live in a really cold or hot climate, then the advantages of synthetic are minimal. I use it because I live where the winter temps are often below zero and it really aids the cold cranking. I also change my oil at 5,000 miles rather than 3,000 and like the extra margin tha synthetic gives. However, if you change your oil every 3,000 you will do fine with any top quality conventional oil ... I was partial to Castrol before I started using synthetic.

Matt