Patman
Staff member
I was wondering if the pour point of an oil changes drastically from new oil to used oil? If a new batch of oil has a pour point of say -40F, will it end up being -30F after 3000 miles?
quote:Actually the 5w grade is determined at -30C and it has to be less than 6600cP viscosity. 10w has to have a viscosity of less than 7000 cP at -25C. http://www.tosco.com/internet_pub/repository/lubes/44_tn3_4.pdf It's on page 8. And it you look at the cSt of for example Mobil1 @ 40C, 0w30,5w30, and 10w30 are all very close. Which is why I don't understand why people in warm climates would even consider a 0w or 5w-30.
Originally posted by Patman: ...Besides, the lower weight number (the 5 and the 10) are viscosity equivalents at 40 celcius, and I believe that at the much colder temps the viscosities of the two oils are a lot closer...
quote:Well I'm not quite sure. But nowadays I think that all oil of the respecitive grade will flow at those temp. The CCS test doesn't measure flow anyway so it wouldn't matter. Bob's site has a short explanation: http://pub27.bravenet.com/faq/show.php?usernum=2240725418&password=&catid=1381&action=showcat#question8 Maybe someone else can quantify the centipoise numbers. I really don't know what it means, is 7000 thick/thin/average? I would guess that they would at least set the ratings where a real engine could be turned over at that temp. And as you can see each grade is only 5C difference. So there really isn't that much difference. E.g., a GM owners manuals say 10w30 is ok to 0F, a 15w should be good to approx 10F. So it really isn't THAT THICK. Because I have seen people balk at someone putting a 15wX oil in a new car...but it really isn't that big of a deal. I'd even feel fine using it in the winter if it wasn't extremely cold. In fact I did use Mobil1 15w50 in my car in the winter with good results.
Originally posted by Patman: How could the weight be determined at -30c when some dino oils don't even flow at that low temp though?