no real difference in outside temp.. i put in same grade fuel too.. only difference was the gas station had signs everywhere saying the gas contained up to 10% ethanol.. i know 200 is pretty standard, its right in the middle of my gauge on the dash so im not really concerned... just kinda curious as to why the sudden jump, because up until this weekend my temp was like clockwork in a 2-3 degree range and all of a sudden it jumped 10-20