5w-30 cst

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Do car manufacturers know the fact that 5w-30s (besides PAOs) shear to a 20w by then end of the OCI?

Since I can't quite justify spending the money on Amsoil or Redline, I was pondering on the idea of running a Group III 10w-30 in my 2009 Nissan that call for 5w-30. And I wouldn't hesitate to use it in my Ford that calls for 5w-20 after seeing the UOA thread where the OP used 5w-20 in his Mustang.

I live in an area where it's above 32F at least 11 months out of the year, so the cold start benefits of a 5w probably aren't seen anyway.
 
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First oil shear is not as common as it once was with the higher quality VIIs that are used today in top brand oils.

Secondly, when a manufacturer spec's an oil or oil grade there is an allowance of at least 15% for viscosity loss before the oil would be condemned.

Thirdly, the low VI 10W-30 grade is largely obsolete with synthetic oils since the 5W-30 grade is so shear resistant.
Buying a syn' 10W-30 is therefore a poor value.

Forthly, the main advantage of 5W oils over 10W oils is their higher VI meaning they are lighter on start-up at all temp's not just below freezing. And that also is the main benefit of 0W oil over 5w oils; this advantage aplies even in the summer.

Finally using a 30wt oil when a 20wt is specified acheives nothing other than reduced performance, lower fuel economy and increased wear on start-up.
 
Originally Posted By: semaj281
the fact that 5w-30s (besides PAOs) shear to a 20w by then end of the OCI?

Really, that's fact? Different 5W-30 oils shear more or less and it's different per vehicle/engine too. For example, in my Nissan's QR25DE, Castrol EDGE (i.e. original formula) sheared more than Pennzoil Ultra. However, the UOAs I had done showed them both to be in-grade still.
 
Originally Posted By: barlowc
Originally Posted By: semaj281
the fact that 5w-30s (besides PAOs) shear to a 20w by then end of the OCI?

Really, that's fact? Different 5W-30 oils shear more or less and it's different per vehicle/engine too. For example, in my Nissan's QR25DE, Castrol EDGE (i.e. original formula) sheared more than Pennzoil Ultra. However, the UOAs I had done showed them both to be in-grade still.


How do you know they sheared more? Castrol Edge (SM) 5w30 is thinner than PU or PP in the first place. Did you do look at the starting 40c and 100c viscosities? Just checking;)
 
Originally Posted By: chubbs1
How do you know they sheared more? Castrol Edge (SM) 5w30 is thinner than PU or PP in the first place. Did you do look at the starting 40c and 100c viscosities? Just checking;)

Yep, I compared against their spec viscosities. While EDGE is a little thinner to begin with, the Ultra stayed closer to spec.
 
Originally Posted By: barlowc
Originally Posted By: semaj281
the fact that 5w-30s (besides PAOs) shear to a 20w by then end of the OCI?

Really, that's fact? Different 5W-30 oils shear more or less and it's different per vehicle/engine too. For example, in my Nissan's QR25DE, Castrol EDGE (i.e. original formula) sheared more than Pennzoil Ultra. However, the UOAs I had done showed them both to be in-grade still.

Most Group III oils failed to maintain viscosity by the time they were drained. I saw your UOA with the EDGE, and your cst was at 8.9. A cst of
These are UOAs and observations that show how easily they shear.
http://www.bobistheoilguy.com/forums/ubb...;page=2#2094467

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1902754

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1931561

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1578935&page=1
 
Originally Posted By: chubbs1
Originally Posted By: barlowc
semaj281 said:
Castrol Edge (SM) 5w30 is thinner than PU or PP in the first place. Did you do look at the starting 40c and 100c viscosities? Just checking;)

Sorry to be pedantic but we don't really know how thick or thin Castrol Edge is compared to other oils of the same grade since they don't provide HTHSV spec's. A lower KV100 spec' could mean it's lighter at operating temp's but not if it's HTHSV is the same or higher.
That's a big negative with Castrol NA, they don't provide much technical info' on their oils.
 
Originally Posted By: semaj281
I saw your UOA with the EDGE, and your cst was at 8.9. A cst of div>

My bad. I was thinking the Blackstone range stayed within grade but is apparently represents "normal" shearing. Thanks for correcting!
 
Originally Posted By: semaj281


I'm starting to believe the 20wt specification for the Modular Fords was made solely for CAFE reasons.


Even if it was, it certainly hasn't caused harm to Ford engines.
 
Originally Posted By: barlowc
Originally Posted By: semaj281
I saw your UOA with the EDGE, and your cst was at 8.9. A cst of div>

My bad. I was thinking the Blackstone range stayed within grade but is apparently represents "normal" shearing. Thanks for correcting!

I'm not a tribologist on any level so I may be wrong about the 9.3 threshold. Someone correct me if I'm wrong.
 
Originally Posted By: semaj281

I'm not a tribologist on any level so I may be wrong about the 9.3 threshold. Someone correct me if I'm wrong.


Google SAE J300 for the numbers if you forget.
 
That UOA is in new Mustang that's still shedding Fe and other metals and will show higher than normal elemental numbers. Nevertheless the UOA is not bad.
You can conclude nothing fom one UOA, least of all that the oil was too light.

The proper way to determine the correct viscosity is with oil pressure and temperature gauges. The info derived from that will tell you the lowest actual operational viscosity that occurred in the engine and how much of a safety margin you have compared to the manufacturer's minimum spec's.
 
Originally Posted By: XS650
Originally Posted By: semaj281

I'm not a tribologist on any level so I may be wrong about the 9.3 threshold. Someone correct me if I'm wrong.


Google SAE J300 for the numbers if you forget.

semaj281 is correct. For a 30 grade, the range is 9.3 to 12.5. For a 20 grade it's 5.6 to 9.3. At least according to this paper.
 
Originally Posted By: CATERHAM
First oil shear is not as common as it once was with the higher quality VIIs that are used today in top brand oils.


What are some of the "top brands" that have higher quality VIIs? Do all of today's SN oils fit this category?
 
Originally Posted By: semaj281
Do car manufacturers know the fact that 5w-30s (besides PAOs) shear to a 20w by then end of the OCI?

It's true. The xW-30 SAE range is 9.3 - 12.5 cSt and the xW-20 range is 5.6 - 9.3 cSt. Almost all synthetic or conventinal 5W-30 shear to around 9 cSt after the first 1000 miles (well before the end of the OCI). Most used xW-20 end up around 8 cSt.

But then why do you care? If your engine runs fine with 10 cSt, it will run fine with 9 cSt or 8 cSt. It's not going to affect your wear. Go with xW-20 for best fuel economy. You don't need 10W-30. Almost all major-brand GF-5 xW-20, 5W-30, and 10W-30 practically have the same viscosity -- in the 7.5 - 9.5 cSt range for used oil -- so, you don't really need to worry. Thinner oil is better for most engines because it flows better, reaching more easily where it's needed and cooling the friction surfaces better.

The only exception is if you have a diesel engine. Then the viscosity becomes important to protect it from abrasive soot particles by keeping the oil film thick enough (thicker than the soot particles). In that case, use a CJ-4 certifed HDEO oil, which has an HTHS viscosity of at least 3.5 cP.

Worry more about the additive package than the precise viscosity. Get a major-brand, premium-line GF-5 oil with a hefty additive package that has good UOAs. That will protect your engine better than a slight increase in viscosity.
 
Originally Posted By: semaj281
Originally Posted By: CATERHAM
First oil shear is not as common as it once was with the higher quality VIIs that are used today in top brand oils.

What are some of the "top brands" that have higher quality VIIs? Do all of today's SN oils fit this category?

It's hard to know for sure and I haven't done a survey of 5W-30 oils as I'm more interested in 0W-XX oils which theoretically are more shear prone as they may contain more VIIs.
But high levels of VIIs no longer translates automatically into a high shearing oil.
Take the Toyota 0W-20 for example. It has the highest VI (214) of any oil available by far and it shears very little. The following is a 10,000 UOA with only 4% viscosity loss:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2415119#Post2415119
 
Originally Posted By: Gokhan
Originally Posted By: semaj281
Do car manufacturers know the fact that 5w-30s (besides PAOs) shear to a 20w by then end of the OCI?

It's true. The xW-30 SAE range is 9.3 - 12.5 cSt and the xW-20 range is 5.6 - 9.3 cSt. Almost all synthetic or conventinal 5W-30 shear to around 9 cSt after the first 1000 miles (well before the end of the OCI). Most used xW-20 end up around 8 cSt.

But then why do you care? If your engine runs fine with 10 cSt, it will run fine with 9 cSt or 8 cSt. It's not going to affect your wear. Go with xW-20 for best fuel economy. You don't need 10W-30. Almost all major-brand GF-5 xW-20, 5W-30, and 10W-30 practically have the same viscosity -- in the 7.5 - 9.5 cSt range for used oil -- so, you don't really need to worry. Thinner oil is better for most engines because it flows better, reaching more easily where it's needed and cooling the friction surfaces better.

The only exception is if you have a diesel engine. Then the viscosity becomes important to protect it from abrasive soot particles by keeping the oil film thick enough (thicker than the soot particles). In that case, use a CJ-4 certifed HDEO oil, which has an HTHS viscosity of at least 3.5 cP.

Worry more about the additive package than the precise viscosity. Get a major-brand, premium-line GF-5 oil with a hefty additive package that has good UOAs. That will protect your engine better than a slight increase in viscosity.

Thanks for the insight.
On that note, I found a handful of UOAs with Group III 5w-30 that still showed 10.3-10.8 cst after 6000 miles.
 
Originally Posted By: semaj281

I'm starting to believe the 20wt specification for the Modular Fords was made solely for CAFE reasons.


Yes it is. You'll get much better lubrication out of a 30wt.
 
Originally Posted By: Merkava_4
Originally Posted By: semaj281

I'm starting to believe the 20wt specification for the Modular Fords was made solely for CAFE reasons.


Yes it is. You'll get much better lubrication out of a 30wt.


It was. In 99 the 4.6 2v was 5w-30. In 2000 5w-20. Same motor. The Aussie spec never changed though with the same motors of the same years.
 
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