I have never personally used MMO, but I know of people that have with good results. Another option if you just want to clean the engine, I would just use Mobil 1 in whatever grade is recommended for your car and possibly change it at 2k, then 3k miles (new filter each time), then once you've done those 2 early OCIs, just go to 5k OCIs unless you do a lot of short trips. M1 is a good synthetic oil, and seems to do a really good job of cleaning. MMO I think is inexpensive, so even if you do go that route, you have nothing to lose. As far as leaks, it is a real possibility at that mileage; why do you want to switch to syn now?