I always use a good quality oil, I buy the good stuff from our local Motorcycle dealership. its Honda 2 stroke racing synthetic oil (blue) all tho its a bit pricey it works for me! I have had used opti-2 and it did fine, something about 100:1 mix that frightens me a little. I only switched to it because of price being cheaper but then reverted back to Honda oil. it smells good for one thing and it matches my bike as well.(lol) as far as marine oil goes, I wouldnt use that stuff, and whoever tells you that you can, well thay can drink it for all I care. I know from experience, a couple customers had brought their bikes to me because their motors were not going full power. upon investigating, one had a crank case bearing freeze up and the other was the needle bearings on the crank were busted like yours! replacement motors were cheaper than rebuilding them. Now I have a little over 5000 miles on mine and it runs as good as the day I bought it!