Back when I had a two smoker opti I used to buy my oil out of Bellingham at the merc dealer there. I could get the opti oil for 70 bucks for a 10 litre jug compared to 140 in Canada. That was when our dollar was at or near par. I also managed to buy a large lot from a fishing lodge that went bankrupt or to four strokes, never heard the story but it was cheap. When that ran out, I just started using off brand TCW-3 oil. Mercury, along with all the people you'll find on internet forums will convince you it's worth paying the large premium for Merc branded oil. It is NOT.