well, from what i can find on Wiki, refining grease from raw petroleum crude takes place in the 350-400 degree temperature range. so i would have to think that the same temperatures would apply in this application. hopefully, nothing i operate will ever near those kinds of temps during operation. i would have to believe that liquid cooling of an engine would also help a lot. since the normal temperature of the engine oil right now is in the 210 degree range, i should be very safe for now, unless something drastic happens.