I just bought a car last night and when they pulled my score they said it was 766!!!
But my score from here is somewhere in the mid 600's?
I DID just pay down my util from 80 to 10% but could that make a 100 point difference in my score??
Yes, that probably made a bulk of the difference assuming it was reported to the bureaus before the pull on the auto loan; however, there are variations in the versions of FICO used, and quite likely when purchasing a car the lender will use what's known as an Auto-enhanced score, which is different than the scores found here which are the basic/classic versions.
Without getting too technical, it simply weights factors differently; say you have a mixed file (like I do, some negative, some positive), and I have lates reported on my credit cards from a few years back, but a spotless auto loan history... my auto-enhanced score will likely be higher were I to get it pulled right now.
On the other hand, when I purchased my own car about a year ago, and I didn't have any auto-loans (or any other installment tradeline for that matter) on my reports, my score was markedly lower than my EQ FICO as found here.
Starting Score: EQ 5 561, TU 98 567, EX 2 599 (12/30/11) Current Score: EQ 5 771, TU 4 758, EX 2 758, EQ 8 795, TU 8 762, EX 8 786 (7/28/17) Goal Score: EQ 5 750, TU 4 750, EX 2 750, EQ 8 800, TU 8 Blah, EX 8 800 (01/01/18)