I have a Merc. 25- 2 cycle. I have been using quicksilver oil in it. I would like to change to a synthetic oil but would like to have a few questions answered. 1.when looking at a synthetic oil, I didn't see any TC-W2 rating. Do synthetics carry these ratings?? 2.Can I switch to a synthetic since my moter has about 200 hr. of usage?? 3.What is the name of a good synthetic oil I can use for my size outboard?? I troll alot in the summer months and would like to do away with all the carbon issues. Any info would be greatly appreciated - thanks 