Castrol is only "allowed" to call Syntech "synthetic" because they won a legal case. It's not really made from a synthetic base stock. Castrol is king of hype and is IMHO responsible for many premature engine deaths with their 20W-50 ad campaign that started in the 70's. In a short nutshell: This was mainly due to the pour point solvents and thickeners crapping out, making the oil WAY to thick for proper flow at cool temperatures.

Anyhow use a real synthetic and stick with 7500 miles (turbos are 10,000 max anyway with the best synthetic oil: Amsoil)

By all means, go with synthetic. Castrol would not be near the top on my list of preferred synthetics. They reformulated and are using a less expensive (and not as good) base stock.

While you could probably run either AMSOIL or Mobil 1 for a longer interval, you shouldn't do that without oil analysis while it is under warranty. Heck, 7500 mile drain is really cheap insurance.

If you use synthetic I would use it for better protection/performance, not to extend the service interval. I am not a fan of Castrol. Had some nasty stuff happen to my Saab with it. If I were you I would bring my own oil to the shop, and make them knock off whatever they usually charge for oil. You can get 6 quarts of Mobile One or Royal Purple for under 30 dollars.

About Castrol Syntech:

http://pub6.ezboard.com/fstocksuperstockforum70108sssclasstech.showMessage?topicID=537.topic

I wouldn't use it.

MAT