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. They would give absolutely no startup flow advantage above freezing temperatures. However some people seem to think they do. Someone on a BMW forum uses 0w30 in Florida because he thinks it protects at startup better and that is the most important. Maybe if he lived in the artic. Nevermind that it is either going to shear back to donkey urine or oxidize and leave deposits more readily. I don't see the advantage. AMSoil did a great job brainwashing with their 0w30 series 2000 "super oil" Edited to change one word. [ July 02, 2002, 11:44 PM: Message edited by: 59 Vetteman ]
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?