what does it all mean? and what should matter?

[lucerne06]

just for giggles I went to castrols website to compare their
GTX Conv. and the GTX HM. looking at the charts between these FIVE grades what do these numbers between the TWO oils really mean. What would be best for a summer or winter use? or a high milegae vs lower mileage engine. Do they all actually(in Grade)flow at the same rates? or is it wise to choose carefully between the tow oils of the same grade for differnt seasons and aplications? And what really do all those ASTM-D tests mean?

http://www.castrol.com/liveassets/bp_internet/castrol/castrol_usa/STAGING/local_assets/downloads/p,q/psd_gtx_usa.pdf

http://www.castrol.com/castrol/liveassets/bp_internet/castrol/castrol_usa/STAGING/local_assets/downloads/p,q/pds_gtx_high_mileage_usa.pdf

 

[Scienceman]

Fixed link #1

]Fixed link 2

 

[lucerne06]

Hey Thanks TROY BUILT

 

[lucerne06]

Castrol GTX GTX HM
5w-30 10w-30 5w-30 10w-30
vis@100c 10.8 10.6 12.0 12.1

vis@210sus 62.1 61.4 66.4 66.8

low temp 6600@ 7000@ 6600@ 7000@
crank vis -30 -25 -30 -25

low temp 40000@ 50000@ 60000@ 60000@
pump vis -35 -30 -30 -30


so the questions remain,,, what is the difference between these two oils?? is one better for summer vs winter? is one better for an old vs new car...is their any real difference in the flow and pumping rates...? how is it determined?

 

[mechtech2]

Thinner when cold is always better.
Thicket at normal operating temperatures CAN be better, if your engine needs it.