Why is "7.5" scoffed at, but 16, 8, and 4 are OK?

Status
Not open for further replies.
Some are on SAE J300 or have been proposed for it. Others haven't.
wink.gif
 
Originally Posted By: gfh77665
Why is "7.5" scoffed at, but 16, 8, and 4 are OK?


16, 8, and 4 are completely pointless.

We like completely pointless in these here parts, stranger.
 
7.5 exists in motorcycle fork oil, but that's an application where 0.5 can be noticed...by those who can notice these things.
 
Who on earth would make a pizza in 7.5" diameter when you can easily make it 8" (or 16" or 4")?
 
The SAE J300 "W" viscosity specs are in ranges...0W, 5W, 10W, 15W, 20W, and 25W....Everything that you mix will fall into ONE of those groups.

SAE (operating temperture) grades now include 8, 12, and 16 as of the last few years, along with 20, 30, 40, 50, and 60...again, everything between 4 and 26.1Cst at 100C falls into one of those grades.
 
Originally Posted By: gfh77665
Clearly arbitrary. Its OK to conjure up the 4, 8, 16 system "just because", but not a "7.5".


You could call it "blue whisper" if you wanted to make up a grade, to sell to your friends...go your hardest, and call it 7.49998W, but don't link it to J300.

But if you want to use J300 as a reference, then use it as a reference, and it's either 5W or 10W...no one is making up the 8 and 12 (where is your 4 ?)...grades which didn't exist until recently, as they all fell into the "20" in it's original definition, but then fell out of it into no-man's land until a working group made them exist.

You can mark up your speedo in parsecs/millenium, then paint speed limit "bands" onto your speedo too if you like...the speed signs on the highwway will still be in MPH.
 
Originally Posted By: gfh77665
Why is "7.5" scoffed at, but 16, 8, and 4 are OK?


Because it's just a grade and not the actual viscosity measurement in cSt. Or are we talking pizza? Because a 4" pizza is definitely too small and 7.5 is an odd size
grin2.gif
 
Last edited:
Here's Honda's offerings when they weren't happy with J300....
https://global.rakuten.com/en/store/t-joy/item/hondaoil_4rin-012/
Honda "Ultra Next"

https://global.rakuten.com/en/store/t-joy/item/hondaoil_4rin-009/
Honda "Ultra Green Hybrid".

I'm proposing a different system.
VIBGYOR for the low temperature end.
V for Violet, being the coldest end of the spectrum, and Red obviously the hottest...calibrated to Earth, so it's sort of a -40C to +40C thing

Will still use HTHS as the second part of the grading, time 10 to make it meaningful.

So an oil that will start at -40C, and have an HTHS of 3.2 would be a V32. A summer oil here could well be a R32, dropping to a G32 or a Y32 in winter.

Of course a cold snap in Canada or Alaska might need better than a V rating, so there will be a -V for those eventualities.
 
Originally Posted By: Shannow
...

I'm proposing a different system.
VIBGYOR for the low temperature end.
V for Violet, being the coldest end of the spectrum, and Red obviously the hottest...calibrated to Earth, so it's sort of a -40C to +40C thing

Will still use HTHS as the second part of the grading, time 10 to make it meaningful.

So an oil that will start at -40C, and have an HTHS of 3.2 would be a V32. A summer oil here could well be a R32, dropping to a G32 or a Y32 in winter.

Of course a cold snap in Canada or Alaska might need better than a V rating, so there will be a -V for those eventualities.


I second this proposal, let's bring it to a BITOG floor vote and hopefully we will see oils with these markings in Walmart by March.

But, rather than having -V in a future standard update, I propose to turn the V upside down and make a lambda...
 
Originally Posted By: gfh77665
Clearly arbitrary. Its OK to conjure up the 4, 8, 16 system "just because", but not a "7.5".


You should think of the W rating like a standard grading system in school (with no + or -), i.e. 90-100 is an A, 80-89 is a B, etc.

So if you score a 90, you get an A and if you score a 100, you still get an A, there are no AB's, AA's, A+, A-, etc. Just A, B, C, D or F.

So not arbitrary. You get a W rating based on the test score, simple as that.
 
Originally Posted By: gfh77665
Clearly arbitrary. Its OK to conjure up the 4, 8, 16 system "just because", but not a "7.5".


You're right - completely arbitrary. Thing is, 20, 16, 8, 4 were proposed and accepted by a "governing body" (no, not government, just a group that can ballot and come to agreement on terminology). 7.5 was not. There is some likelihood that it was discussed/considered.

You can use terms however you want. The presence of a 7.5 or an 8 is practically irrelevant for all intents and purposes; it's just a designator for a range of viscosity. More accurate would be to define the actual viscosity at actual temperature, and know specifically what the units of measure mean (cSt= 1mm^2 / s; does that have any physical meaning to you?). Using something different that was agreed upon by a governing body just makes you look uninformed.

Asking about it is a fine question however, as it's how people become informed, and is the reason for discussion forums.
 
Originally Posted By: gfh77665
Why is "7.5" scoffed at, but 16, 8, and 4 are OK?


Well the first thing, assuming we are talking about the other thread, is that the 7.5 was 7.5W, putting it on the left side of the W, meaning it falls under being defined by the CCS and MRV limits not a range of viscosities like the other grades you mentioned.

Secondly, its got a .5 going on. You'll notice none of the classifications for either Winter or SAE grade in J300 have fractions as part of them.

The number on the right of the W, unlike the one to the left, does actually have a relatively narrow range of viscosities that define it. If the 20 range had been split by 5's rather than into 16, 12 and 8, we would have xW-5, xW-10 and xW-15. I assume that the similarity to the Winter ratings and subsequent confusion that might arise from a 5w-10 or 5w-5 is what led to them using 16, 12 and 8 instead, but I could be wrong on that point, as that's speculation.

Regardless, as J300 clearly shows, each of those designations not part of the Winter rating scheme has a narrow 100C visc range that defines it as well as an HTHS floor:



You can also see that the 100C bottom range for the 5W and 0W designation are the same, and both are lower than the new SAE 8 grade at the same temp. Since the vast majority of lubricants wearing the W designation are multigrades, it is the CCS and MRV limits that are the focus here.
 
It's been said in previous posts, but I think it could be said a little more simply.

Because 7.5 is a made up, imaginary thing that could literally mean anything at all that the manufacturer says it does. I could blend an oil with 1000 cSt at 100C and call it 7.5 if I wanted to. There is nothing at all stopping me from doing that. I'd be in trouble if I called that same oil an 8, 12, or 16 though.

16, 12, and 8 are standard grades that meet specific standards set by the SAE and are controlled.
 
The overwhelmingly accepted premise is that oils HAVE TO be classified by a multiple of 5, 100% of the time, NO EXCEPTIONS!. Any thoughts outside of that constraint, like someone trying to imagine a "7.5" weight, is immediately met with much challenge.

With that in mind, why has no one even QUESTIONED a 4, 8 or 16 weight? Did the rigidly accepted constraints of a 5 system magically disappear without so much as mention? Why did no one challenge the 4-8-16 system. at all?
 
Well it goes to show that those that backed 5 and 10's only, were dead-wrong.
I've been mixing-up 7.5s and 2.5s for years..... actually multiple decades on the 7.5
 
Status
Not open for further replies.
Back
Top