No 12% oil content should not be a problem; I do not like running any higher. The only reason I mentioned it was I have seen people running up to 18% with a lot of problems with one ways. I know that some times when your one way goes to slipping you can clean it and it helps. How many gallons do you have on your OS 18? On the play in the CB I like to make it where I have just a very little but still spins free. I all so recommend if you are running the stock set up for the RTR to change to the Savage or MT SS set up as I recommended before.

Need to change the gearing on my MT as 13CB and 49 spur is way to low for my OS .18 TZ. I all so found out the first thing I do not like about my Spektrum which was my fault there is no low battery fail safe for the receiver. Yes my MT with the TZ ran off in to a chain link fence but nothing broke.