I disassemble my seats S3 because of the same problem. The heating is attached to the foam, but come off easily.Where has blown heater was obvious clearly, and I just reconnected again using clamp cables.
Currently using ENEOS Premium Ultra 0w50. The only complaint that I have for it is the price. I notice the relatively high consumption of oil even though I exchanged valve seals. I want to try a different type of oil (with different viscosity) but I still have not settled on more appropriate...
I believe it would be better for you to read a little about automotive oils, their properties and what it means numbers, which indicate the viscosity.
Motor Oil Viscosity Grades Explained in Layman's Terms
The difference between the ATE57 and ATE54 is in the size of the piston. Digits determined size of the piston in millimeters. Although at first glance the difference is small, the increase in braking is great. I drive my S3 with the following setup:
Front ATE 57+ EBC GD931 + EBC Red Stuff +...
For here (Bulgaria) time is rather large temperature range (from -15 to +37 degrees Celsius) I use 5-40w but I decided to try another oil with a wide temperature range. At the moment I put 0-50w, but I passed quite a few miles to give correct opinion.