Cool Runnings 2.2 CRD

My Cruiser felt hesitant in cold weather until the engine had warmed up. I did a leak off test on the injectors and two of them leaked off 20% more than the other two. I sent the suspect injectors for flow bench testing but the results were OK. United Diesel did however mension that the deposits on the injectors looked as though the car had been using bio diesel. A local garage sells bio diesel at the pumps, and when I switched to using it the cold running problem disappeared, and there was no difference between injectors when I re ran the leak off test . I can only assume bio diesel is thinner in cold weather ?
Doing the 'Boy Racer' mod of adding a resister to the IAT sensor, to fool the PCM into thinking it's colder than it is, may have worked too, but I haven't tried this.