Originally Posted By: 1JZ_E46
Originally Posted By: edyvw
Same base oil. Difference will be in lower NOACK in 0W30 of 8.3% compare to 9.1% in 0W40. HTHS is better of course in 0W40. If you do primarily city driving, 0W30 might be bit better as it will have bit better flow around city oil temperatures. However, considering price difference I am not sure is there any common sense to get it. 0W40 is thin W40 oil. 0W30 has cst of 12.1 while 0W40 is 12.85. Not much difference at 100c.
If 0W-30 were cheaper and easier to find, I would use that over 0W-40 in my X5. "As thing as possible, as thick as necessary," right? The 0W-30 probably has less VII, hence the better NOACK and slightly thinner KV100.
Well, depends on application. If you pushing gasser hard, maybe W40 is better. For combined driving, 0W30 is better.