well matt the reason I say it seems really high is because on my pressure nossel heater I run a preheat before the pump @ 120 f to take load off the pump, then just before the nossel I bump it up to 180 f and the combustion and spray pattern are great, but I suspect with synthetics it would need to be alot higher. Now the problem with Used motor oil is that there s alot of additional carbon in the oil and as far as viscosity 180 will usually bring it to the equalant of #2. But I remind everyone, that we are here to discuss , learn and find out what works the best with little to no problems, so If it works for you with no nossel probs, cool. Maybe I'll try to keep bumping the temps up too...although like most fuels it only takes atomization and ignition at the right viscosity.