I remember back about 10 years ago, Traxxas said to break in their .15 engine with 4 tanks of fuel driving slowly with the body off. I did that and the engines lasted a long time although I did eventually wear out each of the engines on my TMaxx, Nitro Rustler and Nitro 4-Tec. In contrast, when I bought my Losi Ten T about 3 weeks back, the instructions just said to take it easy for the first couple of tanks and not go full throttle. I noticed that on the first 4 tanks, taking it really easy, going about 1/2 to 3/4 throttle it would heat the engine up to just past the safe zone (190-230 degrees), at which time the telemetry on my radio started warning me. I stopped until the engine cooled down to about 100 degrees and started again. Since about the 6th tank of fuel, the engine warms up to about 190 degrees and pretty much stays there, give or take 5 degrees or so even going full throttle on grass! I took the precaution of running Blue Thunder First Run fuel for the first quart (about 10 tanks full) and just this weekend switched to 20% Losi Nitrotane (expensive stuff, 15 bucks a quart). When I first got the truck all I did was richen the mix with the HSN about an "hour" or a 12th of a turn. I haven't moved it and the car is now a rocket with the engine starting every time and no increase in temp at all. I would say with these new engines, you just need to run a tad rich, take it easy for the first few tanks and don't go balls out. I also highly recommend the Blue Thunder First Run fuel.