None of the simulators, including the myFico one, seem to use my actual data, even though they have it as I had just pulled my reports through them before trying it. I had no installment loan, so adding an auto loan would clearly add more positives than negatives from what is commonly known about how Fico scores work, and in fact, I got a great score jump doing so. But all the simuators all had me loosing points instead. All my major negatives are falling off after 7 years in the next few months, but non of the simulators seem to recognize that when I tried to simulate aging my report 6 months or simulate paying my bills on time for the next 6 months.
So don't base any credit decisions on simulators. They only are accurate in a general sense. You generally do this, and you'll generally see that. What they won't do is actually be accurate for your specific credit profile.
