First time I am doing an oil change on my car (recently bought). What type of oil should I use? I was reading that I should use Mobil 1 0w-40 or Castrol 5w-40.

Car: 2000 Audi A4 1.8t Quattro with 103,000 miles

Thanks

 

either one of those should be fine as long as it is "fully synthetic"

 

When the audi dealer did my oil, they said the engine only called for semi-synthetic. I asked about full synthetic and they said that if the car hadn't had full synthetic for its whole life, it could do more harm than good. is this true?

 

It's partially true... Once you put in full synthetic, never go back. If you do put in something other than full synthetic supposedly harm can be done.

 

I use Castrol 5W40. I've read that it's what Audi uses at the factory. A lot of people use Shell Rotella T6 Synthetic. It's on sale right now at autozone for $20/5+quart jug as opposed to 38ish for Castrol. I'm going to try Shell next.