Border crossings
Well, i live 10 mins from the Border in Houlton Maine,i'm over there twice a week for whatever,usually Ebay products since a US mail box is $20/year at mailboxes plus.They accept all those large orders like (TIRES) for a small $4 Handling Fee.I also found that alot of US companies weren,t interested in International shipping.When i go to get a parcel at the mailboxes plus,theres always at least 100 Tires sitting outside for Pickup from canadians.
Be warned though, they will check at the Canadian Border for speccial CSA approved tires,if you have them on already and they don,t meet the requirements,you WILL be turned back to remove them,plain and simple.As for the smuggling them over,hmm,there are border guards who specifically watch the shops like V.I.P and Walmart garage for Canadians doing just that,believe me I KNOW!, its not worth it for all you save time you pay 7% US sales Tax,13% Canadian Tax,15% Duty(Perelli,Michelin)and 10% Exchange rate.Stay home spen the money in your own country,also warranty is only Valid if you take the Bad tire back to where you bought it.
As for Oil in seadoo's, go to your local Seadoo shop, ask if they sell in Bulk.Get a 2 Gal Jerry can, tell them to top her up with XP-s for $40/Gal, same price as Quicksilver at Walmart in Canada ($25-Gal USA Walmart)