Originally Posted by jspauld2
The "black goo" as everyone calls it is very typical of break-in. Most of the "goo" for the first several tanks is actually little pieces of metal that are wearing away from the surfaces that are being mated by the break-in process. The "goo" should decrease a fair amount and change more from black to a lighter brown after the engine becomes more broken-in. It won't go away altogether though because there is too much oil in the fuel. As the engine breaks-in it changes from being small amounts of metal to being un-burnt oil - hence the change in color and amount. The reason you don't see so much residue from the larger airplanes is mostly due to the lower oil content in the fuel. If you redirect the exhaust you can greatly reduce the amount of residue actually on your airplane.
Horizon Hobby, Inc.
Saito, Evolution & Zenoah Developer
And thank you Jimmy for your response. No doubt that with something new, we each apply our personal wish list as to what it will do for us. Certainly there will be much less exhaust residue from six oz of 5% oil additive fuel compared to 12-14 of 18%.
Additional steps to divert aren't as problematic on these size planes and we'll give effort to that end and see how it goes.