Estimated oil consumption is approximately 200 ml per 1000 miles. 'Guzzle' might be considered an exaggeration. When queried, Triumph GB claims the consumption to be well within the industry standard of 1000 ml per 1000 miles. Nevertheless, 200 ml per 1000 miles is far more than I am used to.
TS660 purchased from Fowlers and they are conveniently located for me while in the warranty period.