GC 0-30 mix

[delta901]

I have about 40qts of GC from AZ clearance 2-3 year ago. I will use them in my Lexus ES300 1MZ-FE with 75k on the clock. AFAIK, GC 0-30W is actually a low-40 grade. I want to get a low-mid 30 grade.
Which grade should I use to mix?

0w20
5w20
5w30
10w30

OCI is 5k due to stop and go traffic 10mi one way.

Thanks!

P.S. how can I determine if one oil is a low x grade, mid x grade or high x grade.

 

[PT1]

0w20 or 5w20

 

[ericthepig]

Mind your Ps and Qs with that 1MZ-FE (and keep it topped off). Tricky engine it is.

 

[hillclimber]

Originally Posted By: delta901
P.S. how can I determine if one oil is a low x grade, mid x grade or high x grade.


Read the manufacturers specs and look at the viscosity given. Here's some info on Castrol Syntec products:

http://www.castrol.com/liveassets/bp_int..._syntec_usa.pdf

Look at the viscosity figures on page 2, 100 degrees Celsius, cst. You can clearly see how the viscosity varies by weight.