5W30 Dexos vs. 10W30

[camrydriver111]

Which oil is superior 5W30 synthetic or 10W30 synthetic? Let's say they are the same brand.

I hear a lot of people saying dexos certification is really important, but you can't get dexos in everyone's favourite 10W30.

5W30 is dexos certified, but 10W30 has low viscosity spread. What is more important?

 

[Greasymechtech]

Important? Superior? Depends on the actually spec's and performance of the oil.

 

[Garak]

Originally Posted By: camrydriver111
5W30 is dexos certified, but 10W30 has low viscosity spread. What is more important?

Particularly when using a synthetic, I'd stick with the 5w30. It certainly can be helpful in our climate, and there are few modern certifications for gasoline 10w30s, other than SN/GF-5. Next time you're at Canadian Tire, see if your locations got rid of the 10w30 synthetics. There aren't many of them left here.

There are, of course, other 5w30 synthetic options that aren't ILSAC or dexos1 rated, and are very robust, that I'd pick before an ILSAC 10w30 synthetic any day of the week. I would suggest that Delvac 1 LE 5w30 is more shear resistant, thicker at operating temperatures, and has better cold weather numbers than almost any ILSAC rated 10w30 synthetic I can think of, and for a significantly lower price.

 

[HTSS_TR]

Most vehicles with xW30 are usually have 5W30 as recommended, few models with higher performance engine such as Honda S2000 10W30 is needed. The main reason is lower Noack.

Some 10W30's, conventional and synthetic, have Noack around 5-6& while 5W30 of the same brand has 10-12% Noack.

 

[Ducman]

Originally Posted By: camrydriver111
Which oil is superior 5W30 synthetic or 10W30 synthetic? Let's say they are the same brand.

I hear a lot of people saying dexos certification is really important, but you can't get dexos in everyone's favourite 10W30.

5W30 is dexos certified, but 10W30 has low viscosity spread. What is more important?


It's not possible to get a dexos oil in 10w30 grade period.
This history behind this dates back to about 2006 when GM made the decision to simply exclude 10w30 grades from the approval process for the relevant specifications at the time(GM 4718M and GM 6094M).
This laid the foundation for the later dexos spec oils not being any thicker than 5w30 grade.

In real terms, there's no measurable difference in performance between these two grades.
The only exception being for very low temp pumpability if required, and as stated previously by others the noack is marginally superior with the thicker oil which is always an advantage.

The difference in the viscosity spread between the two oils is probably of no consequence over the normal service life of the two grades, when used in the relevant modern GM engine designs.
This is why some people understandably regard the 10w30 grade as being redundant.

I personally prefer to use the 10w30 grade(as specified in my owners manual for my 2006 HSV GTO) as I regard it to be a better choice for my warmer climate here in Queensland, Australia. Price and availability is the same in my preferred brand of oil.
There are absolutely no pumpability issues evident in my climate, although I will concede there will be an immeasurable improvement in fuel economy for the first 1.5-2 Kms of driving in cold winter weather.

 

[camrydriver111]

So any dexos oil will also be ILSAC correct?

If I am buying quality oils I shouldn't worry about dexos, however if there are questions about oil quality I should go for dexos? For example if I am in the middle of nowhere and I need a quart to top off and they only have convenience store oil.

Originally Posted By: Ducman
In real terms, there's no measurable difference in performance between these two grades.


What about shear resistance? If I am going for an extended OCI (~20k miles) would there be a difference?

 

[Ducman]

Shear resistance over an extended OCI?
The thicker of the two grades may have an advantage.
With what you are proposing regarding the extended OCI's, rather than being fixated on minute differences in viscosity I would be focusing on an oil with a very high TBN.
Amsoil SS comes to mind in both grades.

Just pick a grade that's appropriate for your climate and application and run with it.(refer to your owners manual)
Do a few UOA"s to confirm the oil's service life.
You could even change viscosities if it's within reason or allowable limits and report back to the forum how you are going with it.

Do you have a GM vehicle hence your enquiry about dexos oil, or is it a Camry?

 

[SR5]

Looking at the spec sheet for two mineral ILSAC GF-5 oils, they are from Penrite, but I assume typical examples.

Grade - Vis 40C - Vis 100 C
10W30 - 72 - 10
5W30 - 66 - 11

For a full synthetic Castrol Edge you get
5W30 - 72 - 12

The GF-5 oil are energy conserving, so a HTHS of between 2.9 and 3.5

The Edge is a A3/B4 so a HTHS of 3.5 or more, in this case it's 3.6

So you can see the synthetic 5w30 A3/B4 oil is a thicker oil than the 10w30 GF-5 oil.

 

[Garak]

Originally Posted By: camrydriver111
So any dexos oil will also be ILSAC correct?

Yes. I don't believe it's technically necessary. A blender could formulate a dexos1 oil and not bother with with API or ILSAC certification and bottle it as GM service fill (or factory fill) alone, but that could eliminate other customers and would be pretty pointless. For someone trying to sell oil at a Walmart or parts store, it would be suicide.

For a 20,000 mile OCI, one might have to exhibit a little caution. A basic dexos1 blend may not necessarily be up to the task.

 

[ALR]

I had a 95 Z71 chevy, dealer put in 5w30 on an oil change, truck had 100k+ miles on it. My oil pressure kept dropping at idle and very low. Genius friend told me that if 10w40 is used in an engine designed for 5w30 and engine issues arise in warranty, it will be voided because correct oil vis was not used and they can tell what was used as it increases the clearances using wrong vis. My friend is very knowledgeable in this area as he studies it hard and his engines prove it. This is what Ive been told and proven to me after changing oil back to 10w40 oil pressure improved dramatically to 'normal'.

 

[donnyj08]

Originally Posted By: HTSS_TR
Most vehicles with xW30 are usually have 5W30 as recommended, few models with higher performance engine such as Honda S2000 10W30 is needed. The main reason is lower Noack.

Some 10W30's, conventional and synthetic, have Noack around 5-6& while 5W30 of the same brand has 10-12% Noack.


+1

 

[Justin251]

Originally Posted By: ALR
I had a 95 Z71 chevy, dealer put in 5w30 on an oil change, truck had 100k+ miles on it. My oil pressure kept dropping at idle and very low. Genius friend told me that if 10w40 is used in an engine designed for 5w30 and engine issues arise in warranty, it will be voided because correct oil vis was not used and they can tell what was used as it increases the clearances using wrong vis. My friend is very knowledgeable in this area as he studies it hard and his engines prove it. This is what Ive been told and proven to me after changing oil back to 10w40 oil pressure improved dramatically to 'normal'.


Oh really?

 

[Garak]

Well, one thing I will note is that GM had specific warnings against using 10w-40 in their engines for a number of years. Voiding a warranty is obviously another matter, but GM had been pushing 10w30 and then 5w30 for many years.

 

[SR5]

The OM for my GM car says use a 10w30 or a 15w40.

I think some of the old 10W-40 mineral oils were heavy in VII polymers, and this caused contamination problems. So GM wanted to avoid these.

I would have no problem with a high quality synthetic or semi-synthetic 10W-40 with less VII or a higher quality and shear stable VII package (such as in a HDEO or Euro A3/B4). Infact that's what I'm using now.

As Ducman mentioned above a 10w30 should have less VII (viscosity index improvers) than a 5w30, and similarly a 15w40 should use less VII than a 10w-40. Given the same base type ( eg mineral oil) the narrower the viscosity range the less VII is required, which I think is good. It's not so simple with full synthetics as their higher viscosity index (VI) give them a greater viscosity range (as in xW-y) with less VII.

A low winter rating eg 5W is better for cold starting below 0F. But a narrow viscosity range usually implies less VII and a lower NOACK volatility and better shear stability. Which is the better oil also depends on oil base type and add package plus on your climate and application.

I'm following the lead of Ducman and Shannow on this and getting the narrowest viscosity oil range I can, while being realistic on how cold my winters really are and how much sub-zero cold flow I really need (not much). If I lived in a different climate, I would probably get a different oil, as I would have different concerns.

 

[Gokhan]

Originally Posted By: camrydriver111
Which oil is superior 5W30 synthetic or 10W30 synthetic? Let's say they are the same brand.

I hear a lot of people saying dexos certification is really important, but you can't get dexos in everyone's favourite 10W30.

5W30 is dexos certified, but 10W30 has low viscosity spread. What is more important?

It's almost silly to run a 10w30 synthetic. The amount of VIIs in 5w30 (and 0W-20) synthetic is minimal -- just a few percent. NOACK of good 5w30 synthetics are under 10% and that's all you need. On top of that, you get far better viscosity index and cold viscosity with 5w30, also with improved fuel economy. It's no brainer to use 5w30 if you will go with synthetic.

 

[SR5]

Yep, must agree with Gokhan.

With a full synthetic I would go a 5W30, already a low VII oil.

For a mineral or semi-synthetic I would go a 10W30 oil.

 

[donnyj08]

Originally Posted By: Gokhan
Originally Posted By: camrydriver111
Which oil is superior 5W30 synthetic or 10W30 synthetic? Let's say they are the same brand.

I hear a lot of people saying dexos certification is really important, but you can't get dexos in everyone's favourite 10W30.

5W30 is dexos certified, but 10W30 has low viscosity spread. What is more important?

It's almost silly to run a 10w30 synthetic. The amount of VIIs in 5w30 (and 0W-20) synthetic is minimal -- just a few percent. NOACK of good 5w30 synthetics are under 10% and that's all you need. On top of that, you get far better viscosity index and cold viscosity with 5w30, also with improved fuel economy. It's no brainer to use 5w30 if you will go with synthetic.


+1, the only time I use 10w30 is if i get it on clearance.

 

[Georgiey22]

I recently purchased 3 jugs of Valvoline Synpower 10W30 on clearance and will use on my 2005 GTO and Chevrolet Silverado in Southern California with no concern whatsoever. In fact , looking forward to it!

 

[Garak]

Originally Posted By: SR5
I think some of the old 10W-40 mineral oils were heavy in VII polymers, and this caused contamination problems. So GM wanted to avoid these.

Yes, that certainly was the issue. I don't know when GM got rid of the specific warnings about 10w-40 in their manuals, though I believe they still warn against "other" viscosities. I always find it unique how GM was one of the first of to really push the RC 10w30 and 5w30 grades, yet stayed away from the 20 grades longer than almost everyone else.

 

[hatt]

I don't see any reason to run a 5w30 over a similar 10w30 in a warm climate. If you're at all concerned about VII and Noack the 10w30 is going to win. The fuel economy gains in a warm climate aren't going to be measurable.