Originally Posted By: Linctex
Originally Posted By: OilUzer
for example mixing Pennzoil platinum full synthetic 5Wx30 with 10Wx30
does it produce PP 7.5Wx30 (based on Pennzoil standards).
It's kind of tricky...
You'll hear guys on here talking about "a Heavy 30" versus a "Light 30"
You have to really look at the viscosity numbers.
YES - a 7.5W-30 does exist - BUT
If it is (and I'm generalizing a lot here) :
7.499 or lower, it GETS LABELED as a 5W-30
7.501 or higher, it GETS LABELED as a 10W-30
See how that works?
So really, The
numbers don't lie (but the labels kind of, sort of
DO)
It is not tricky at all.
The 7.5W rating does not exist in SAE J300. You are just making this far more confusing for the OP than it needs to be, and for what purpose?
The Winter designation is primarily defined by the oil's ability to pass the CCS and MRV tests over a series of incremental maximums at 5C intervals with corresponding progressively lower W ratings. The lowest rating the oil is able to pass both tests for determines its classification.
To produce a 7.5W rating you would first have to get the SAE to agree to it. Which they won't. Then, they would need to split the 5w-xx and 10w-xx designations, which leaves us with half-degrees, which is just asinine.
Oh, 5w-xx has to pass the CCS test at -30C and 10w-xx at -25C? Well the new-fangled 7.5W has to pass it at -27.5 and has a limit of 6,400cP.
5w-xx has to pass the MRV test at -35C and 10w-xx at -30C? Well our fantastic new Winter half-rating has to pass it at -32.5C
There is no "missing piece" in the W-rating system that requires some half-increment to add more nuance. Either it passes 5w-xx or it doesn't. If it can pass 10w-xx but not 5w-xx, then it is a 10w-xx, that's all there is to it. Trying to make this more complex than it needs to be serves absolutely no purpose and will confuse other people that will inevitably read this thread.
