What octane is required in a 1.8turbo voltswagon jetta?

Hi There, I own a 2001 Jetta 1.8T. The minimum octain rating information is located on the inside of the gas cap door, and I believe that minimum is 91octain. This isn't to say that you can't use 87 octain, or regular fule. Doing so however you'll notice a loss in power, and a possible engine nock. The engine nock results from when the detonation inside the cylinder is not as powerful, causing the valves to sound louder. hope this helps.