I have both MVVS and the Evolution 26cc engines. On break-in I used Mobil 1 racing 2T fully synthetic oil at 30:1 for the first two gallons and 40:1 after break-in. MVVS and Evolution support says you must use fully synthetic. I have a tuned pipe on the Evolution and a Pitts on the MVVS. The timing was set by a shorting plug that plugs into the ignition for each setup. I have the Evolution in a H9 Sundowner and the temp is about 180F on the ground at full rpm. The MVVS is not in a plane yet, but on the test bench, it is almost exactly the same as the Evolution. I would run it at max rpm and check the temp, if it is in the high 200 or more, I would send it to Horizon for them to check. I sent my Evolution 26 in because it leaked out the front bearing, they repaired it and even paid the shipping both ways. It does not leak now.