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10W-60 Synthetic Oil - Good or Bad Idea?

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10W-60 Synthetic Oil - Good or Bad Idea?

 
Old 02-01-2017, 02:43 PM
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Dear shind3,
It looks like your whole confusion is based on the viscosity chart you posted.
As far as I can judge that chart is old and does not show multi grade oils as it lists the "W" oils under the "no W" oils.
This was true before multigrade oils were on the market.
The 5W in a 5W-20 oil today IS NOT THE SAME as the 5W in your chart.
Please read my post about what it does mean.

Oil film strenght depends on viscosity, yes.
It also depends on the temperature of the oil, as hotter oils get thinner.
Remember the HTHS?
That's measured at 150C, not at 100 C where the kinematic viscosity is measured to determine the SAE grade you see on the bottle, like (5W)-30.
Can you imagine a full syn 5W-20 oil, 9cSt @ 100C (that's why its labelled a 20) with a HTHS of 2.7cP @150C?
Compare it with a dino 10W-30, 12cSt @ 100C with a HTHS of 3cP @ 150C.
So here you have a "thin" and a "thick" oil but the properties when it matters (HTHS @ 150C) are almost the same.
Maybe, in the near future, 20 weight oil will reach the HTHS values of old school 30 weights.
Maybe they already have...

A thinner oil at 100C will allow more oil through the engine at higher rpm, so it refreshes/supplies the journals with more oil, so the oil in there stays in there a bit shorter so it doesn't get that hot so it doesn't thin out that much and because it doesn't thin out it has a higher film strenght.
See?


You actually DID state that in the xW-yz nomenclature, the number before the "W" is a viscosity in cSt. @ 40C.
Read your post, #16

Before multi grade oils were on the market there were winter and summer oils.
I'm not old enough to remember those days and if those winter oils back then were actually labelled "W".
With the introduction of multi grade oils SAE kept (or put?) the "W" on the label.
But, as far as I have red on BITOG, no one at SAE will confirm the "W" used today actually (still) stands for "Winter".
A lot of people think it does and in your case, in combination with that chart, was the cause of your confusion.

One can post graphs, charts and numbers all day long but one has to understand what they mean.

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Old 02-01-2017, 10:37 PM
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Originally Posted by SpitfireS View Post
Those are facts, clearly defined by SAE J300.
You are wrong with your explanation.
Period.

Do thin oils, like a xW-20, compared to xW-60, protect worse?
No.
It's about (and you did mention it) the HTHS.

And about the HTHS you need in an engine.
HTHS is also a viscosity (cP), measured at 150C.
When oil is sucked into a journal bearing it heats up very quickly.
And heat means it gets thinner.
If it gets too thin the oil film will break under the high load in that journal bearing and parts touch eachother.
This is bad.
The HTHS number shows how thin the oil is at 150C.
Is thicker by default better? No.
If your engine is designed around a HTHS of 2cP for example and your oil can produce 2,8 at 150C, an oil with a HTHS of 4cp will not protect better.
You have to keep an eye on shear stability though, as oil straight out
Is using a 60 weight oil bad?
Well... it could be.
As I mentioned, your oil pump has a bypass.
That's because the oil pump is a positve displacement pump, which means if the outlet is blocked it goes BOOM.
The bypass is a safety valve, a springloaded piston.
Piston area x oil pressure = force, if that force exceeds the designed limit the valve will open and dump oil back into the oil pan.
The more engine rpm = the more oil pump rpm = more oil pressure.
The thicker your oil, the higher the oil pressure produced by the oil pump.
Combine the 2 and you will see a thicker oil makes the bypass open at a lower engine (=pump) rpm.
So a 60 weight oil makes your bypass open at a lower rpm, that is not good.
There have been posts on s2ki from a German S2k owner saying he damaged the engine using Castrol Racing (!) 10W-60 in his S2000 and driving fast (high rpm) on the Autobahn.
Yes, just the one (or 2 posts) but still.
The F2x does not need a thick oil.

I've seen more than one post on BITOG (and they KNOW about oil) showing 10W-60 oils sheared down pretty quickly.
Quickly means within 1500 miles or so: they are not very shear stable at all.
That data is from a while ago though.
Still I would never ever recommend a xW-60 oil for any S2000.

The F20 can do the RPM based on this:
A very stiff engine block.
A roller rocker (= low friction) design.
Yes, the high lift cams next to the normal cams (VTEC system)
A well designed intake.
An OEM high flow cat, a metal foil cat to be exact.
And last but not least the low friction FRM cilinder liners.
They allow the piston speed at 9000 rpm.
I don't think the oil pump has too much to do with it.
It is a high output pump to supply the oil jets with enough oil at 9000 rpm to keep the pistons cool.
wow dude! U really know our engines well! Reading what u said about the F20's inner workings makes me so proud. King of the VTEC's and all NA 2.0 FOUR BANGERS I am sticking to 5/40 fully synthetic oil. Edge Titanium works well or Mobil 1 as an alternative I'd like to try. So glad for responses like these before I ended up going for 10/60 on an ill advised notion. Thanks.
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Old 02-02-2017, 12:13 PM
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Originally Posted by RolanTHUNDER View Post
wow dude! U really know our engines well! Reading what u said about the F20's inner workings makes me so proud.
This is where I got it from:
http://www.s2000.org/articles/f20carticle.pdf

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Old 02-03-2017, 01:57 AM
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Originally Posted by SpitfireS View Post
Coolio

Call me paranoid (okay I am paranoid) but is it totally safe to lower my VTEC to 4000RPM on 5W/40 oil??
Others have said yes and I believe them no doubt but, just felt the urge to ask again, lol
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