I swear, some of you guys are giving out stupid advice thats going to make someone else blow up their engine...... Dude54325, so far your advice has been pretty much incorrect and of no help, I own an STS .30 and know 15 others who run them too now listen: During break in, it is ok for temps to hover over the 270 range, as long as its under 300F you are ok. I broke mine in without a temp guage as I have done with all of my engines, throw it in the toolbox, you dont need it! Do not do the pinch test, that is a Traxxas noob mistake... What you want to do is set the high end first, make sure its not hesitating at top speed and not flaming out. Now when you set the low speed, you want a nice strong take off with no bogging. An indicator of a lean condition is a gurgling sound at idle, it sounds unstable and rough. Make sure you have at least a gallon on the engine before leaning, I just ran mine this sunday in dragracing practice and it tops out at 48MPH with my racing HPI Savage 25. Very good engine with the 702 pipe.. Need any more help, PM me or search for the thread "STS ENGINES" in the HPI Monster Truck Forum, 36 pages of knowledge on this mill. Also make sure you shim it after around 1.5 gallons of running. One silver shim for 20% or less, for 30% one silver and one copper. Good luck, Tom[8D]