I've wondered about this for a long time & don't remember if I've ever posted this question on BITOG before. If so, it was several years ago & there was no definitive answer.
Is there a "trigger temperature" that must be reached before the cold-flow properties of modern multi-weight motor oils work at their best? For example(I'm just pulling numbers out of the air here), say the cold flow properties really begin to "kick in" at freezing(32*F, 0*C), and work well enough so that at, say, 40*F the oil is actually harder to pump than it might be at 25* or 20*F?
Or, for a given motor oil, is it simply a case of the colder the thicker?
Here, it *very* seldom drops below 20*F, and with one oil in particular, I noticed that my car seemed to crank & start easier at just over 20*F, after a night-time low of about 17*F, than when the temperature was in the mid 30's to very low 40's. It's been a few years now, but I remember it distinctly because it surprised me so much.
Any hard info available on this?
Is there a "trigger temperature" that must be reached before the cold-flow properties of modern multi-weight motor oils work at their best? For example(I'm just pulling numbers out of the air here), say the cold flow properties really begin to "kick in" at freezing(32*F, 0*C), and work well enough so that at, say, 40*F the oil is actually harder to pump than it might be at 25* or 20*F?
Or, for a given motor oil, is it simply a case of the colder the thicker?
Here, it *very* seldom drops below 20*F, and with one oil in particular, I noticed that my car seemed to crank & start easier at just over 20*F, after a night-time low of about 17*F, than when the temperature was in the mid 30's to very low 40's. It's been a few years now, but I remember it distinctly because it surprised me so much.
Any hard info available on this?
