Cranky/cold start

I recently “upgraded” from a 4 cylinder Ford Ranger to a 1993 4 cylinder Subaru Impreza. It’s actually safe to drive on the now snowy roads of northern West Virginia. I’ve been trying to procure a Chiltons manual for general maintenance, but this is NOT the problem. On occasion in cold temperatures (under 20 degrees) the engine will turn, but not ignite, thus starting the car. On 2 occasions: once at 15 degrees and at 17 degrees, NO Start. Temp raised to 20 degrees, good to go. Car runs great (185k miles, new exhaust, heating system, battery, etc). Temp has since been below 20 degrees again & it will start, but afraid of that day it won’t. Have considered a Katz cooling system that was recommended. Subaru has been no help & a local mechanic who works on subaru’s says “NO, you don’t need that… You wouldn’t need that unless you hit -20degrees. I think it’s a problem w/your ignition.” Seriously? And o.k., say I believe that, when can I bring my car in? 3 wks away… Excuse me!@#$% Any guidance would be welcome.