I suspect Rudy (rcompart) and others here could provide an answer as to what this "lie" would possibly cause the ECM to do. The ability to modify the fan turn-on temperature is there for a reason. If you want your fan to come on earlier, it's the way to do it.

(Or at least a BETTER way to do it).

You know, if I can go farther than -10f, I think I want it on at the same temp the thermostat is set for. No need to let it get any hotter than the thermostat is trying to limit it to.