I went across the border to Walmart for my last oil run. I bought 3 of the Rotella T5 gallon jugs for $15 each. Crazy cheap compared to up here. The border guy didn't care. No taxes. It made for a nice day ride too.
The T6 down there was $23 I think. This is one gallon (4+ litres). Oil lasts forever too, so just stock up and save a bundle.