Since you asked, I'll brag a bit. It has been quite cold here this past week. Last night it was -26C (about -13F I think). After sitting for ~11 hrs, my 1.9 started right up without being plugged in. My compression is in the low 400 range and I use 5w-40 fully synthetic oil which helps a lot. All four glow plugs work and the battery is good. These engines will start quite poorly when cold even if one glow plug is burnt out. I'm sure others here have tales of starting in -30C and lower.