Kmvreter said:"...owners that use the synthetic motor oil live in very, very cold climates and need the quick sub-zero flow quality that the synthetics give you on cold starts."
That's exactly what I sometimes face. I'm not always able to plug in the block heater when I'm away from home (ie. at work.) They don't recommend to go back and forth (syn to dino) from winter to summer otherwise I would just do that. I guess I could suck it up and use M1 full time and hope I get some fuel savings. Does anyone have any actual fuel economy numbers of dino vs. syn? I'm anal for numbers/stats and I track mine. I guess I'll have to switch and do some long term experiments.
If I lived in Canada and my car was outside and needed to be plugged in I would use the synthetic. I doubt you could tell any difference with the MPG.