...because
your car is very well adjusted
In my opinion, junkie plugs though, combined with a weak battery is the good old recipe for morning-time sadness. Especially at -25Celsius!
(-13F)
Generally speaking, it`s not worth saving or experimenting on something that could easily lead to future headaches... A Bosch plug costs $10-18? which is $60-100 for a full set of 6 plugs, proper type, great quality; ... all this to avoid taking blood pressure medication after speaking with the diesel shop. $$$