JeffinTD
Yea, it sure did get off the main subject, but it is sure fun to excersise the old brain and have a friendly debate.

 

Good place to look up terms like kinematic viscosity and pour point: <a target=_blank class=ftalternatingbarlinklarge href="http://www.noria.com/dictionary/default.asp?definitionsearch=xqxqxqxq222&alphasear ch=K
">http://www.noria.com/dictionar...2&alphasearch=K
</a>

To determine kinematic vicosity, oil at different temperatures is dripped through a capilary tube (hum, sound in any way similar to flowing around the channels of an engine????). For example, an oil that is 9.3-12.49 cSt at 100 degrees C would classify as 30 weight, and one that is 12.5-16.29 would be a 40 weight, etc. This is not a measure of shear strength, rather this is how the API determines the viscosity classification of any oil! (Although bulk viscosity of an oil is certainly related to shear strength.)

Pour point is certainly also related to "pumpability", but look at the pour points in your example. Both the 10W30 and 10W40 are -25 degrees....no difference. Yet, one flows through a tube at 70 and the other at 94 cSt at 40 degrees C respectively...which numbers give us the most usefull information????

 

....and why are all these pour points identical, when their viscosities are extremely different? http://www.redlineoil.com/pdf/4.pdf


Does this mean that a 20W50 oil is just as pumpable in the cold as a 5W20??? I don't think so.......

 

<div class="FTQUOTE"><begin quote>Originally posted by: JeffinTDMan, this got way off track from the original topic of 420 EFI starting in cold weather...</end quote></div>

Not really. An engine with the proper (thin) winter weight oil is going to turn over more easily, so it is going to start better....

 

Reconranger
OK explain this one, DO YOU AGREE THAT SYN OILS ARE FAR SUPERIOR FOR COLD CRANKING IN THE WINTER! Sure you do or you wouldn't be using Redline.
Myself I too agree.
Then explain why both of us would choose a 5W-40 syn with a pour point of -50 degrees and a cst of 87.4 at 40C (104 degreesF) over a 5W-30 dino with a pour point of -30 degrees and a cst of 59.7 at 40C (104 degreesF)
#1 the pour point is lower
#2 the cst is higher (sheering strenght) less break down.
If the syn oil has a lower cranking ability then by your calculation the cst should be lower than the 5W-30 dino. No, it is higher, but the pour point is lower.
www.carbibles.com/viscosity.html