I tried doing the same thing a couple of weeks ago, and broke the filter head. I wasn't that big of a deal, I found one at the junk yard for $25. After I put the new one on, I got to thinking that maybe a boat plug in that hole might've worked. You know the plugs that you put in the hole on the back of small boats, and you flip the lever to the side and it tightens down. Put it in there from the inside out, so the pressure in the filter keeps it in. Back to the original question, I've run my truck at -35 this winter and never had a problem without that heater plugged in. We had -25 three days in a row once this winter, and when my truck was idling I could hear it surge, like the fuel was starting a gel up. But it warmed up that day and I never had a problem.Being from Kentucky, you should be alright.