I just bought this car with 80K miles and thinking of changing the oil into synthetic.
Can someone tell me if this is a good idea or not? Which brand and grade should I get? Your help will be appreciated.

 

On previous cars I used Mobil 1 which is compatable with mineral oil. I now use mineral oil 10-30W SL. Audi changed my oil 6 times at 10,000 mi. intervals. Their mineral oil always remained smooth. I now change it every 8,000 mi.

 

There are good synthetic blends best suited for high mileage cars.

 

I just put in a 5w-30 Castrol syntech. Is that good or bad move in my part?

 

It's OK, but not the best choice. Run with it for the next 3000 - 5000 miles and then consider something else.

There is only one thing I can say about Castrol Syntec that may give you reason to think twice.
Castrol Syntec is not really a synthetic oil. Here's why:

Mineral based oils contain different hydrocarbons, some of which tend to crystallize into a waxy material at low temperatures. Pour point depressants are chemicals, which reduce the size of wax crystal formation in mineral based oils. Castrol uses a hydroisomerized process to chemically change these wax-creating molecules. This is good except that they call it synthetic; it's technically not.

 

What would you recommend to use then? I used Amsoil back in 1986 for my Dodge Colt Turbo when synthetic was $15 a litre and my car had a problem in the winter time. I have never used synthetic ever since until now. So, what is the brand that most people here used?

 

Mobil 1 or Royal Purple are both very good synthetics. Purple is pretty expensive and can be hard to find depending on where you are located. Mobil 1 is less expensive and easier to find and as long as you are changing it on a regular basis I don't think you'll see a difference between the two. As for Amsoil, I've never used it myself, but I've read pretty good reviews on it. I've run Purple in my 2000 A4 Avant 1.8t since 15,000 miles. Currently I am running Mobil 1, because it is much easier to get.

 

What viscousity do you recommend if I use the Mobil 1? Should I stick to 5W30 or 15W50?