viscosity modifiers, noack and GM direct injection

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Does one want an oil with low viscosity modifier content especially for direct injection engines?

GM has also decided on 30 wt oil (Timing chains, fuel dilution etc).

For most drivers changing the oil atleast twice a year would fall into the normal category. Then for most of usa you could specify 10w30 for most of the year. For the winters 5w30 recommended by say GM although it likely has lot of viscosity modifiers ? The convenience to customer factor is lost when one has to take the car in for deposits removal costing $$$. So will we go back to old days of 30wt and seasonal oil changes ?
In a way its already been done without advertising it.

Its too bad one cant use 10w30 in new GM during summer and still satisfy warranty.

Can a consumer get some idea of viscosity modifier content of an oil by looking at noack?
 
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I wouldn't look too far into it. GM recalibrated their OLMs to reflect the issues DIs have had with oil. Stick with a dexos1 approved and use top tier fuel and you will be fine
 
Originally Posted By: merconvvv
Can a consumer get some idea of viscosity modifier content of an oil by looking at noack?


The "A_Harman Index" can be used to ballpark how much the viscosity deviates from Newtonian.
 
Originally Posted By: mooferz
Originally Posted By: merconvvv
Can a consumer get some idea of viscosity modifier content of an oil by looking at noack?


The "A_Harman Index" can be used to ballpark how much the viscosity deviates from Newtonian.


Can you give an example using m1 15w50 indicating how much "ballpark" viscosity improvers it employs.
 
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Originally Posted By: merconvvv
Can you give an example using m1 15w50 indicating how much "ballpark" viscosity improvers it employs.

Using the data from https://www.mobil.com/english-us/passenger-vehicle-lube/pds/nausmobil-1-15w50

1. Plug the KV40 and KV100 numbers into the Widman Operational Viscosity Calculator, and calculate a KV150 number.
125@40C, 18@100C: Calculated 7.02 @ 150 C
DF7Iy7X.png


2. Take the density at 15C, and multiply by 0.885 to get an estimate for density at 150c.
0.87 * .885 = 0.76995

3. Multiply the numbers from steps 1 and 2 to get a dynamic viscosity at 150c.
7.02*.76995 =5.405049

4. Divide HTHS by the DV150 number from step 3. This gives the fraction of HTHS to the expected dynamic viscosity of an oil at 150C.
4.5/5.405049 = 0.83256244218

So the Harman index is about .83.

Of course this is just a number without anything to compare it to. I'm not sure if there's a comprehensive Harman index list anywhere, you can find some precalculated in various threads.
 
Ha i feel like i am in school
smile.gif

Thankssss for the detailed example.
My math probably needs to be double check but seems consistent.

So just for fun pp 10w30
.843 at 15c
63.3 at 40
10.3 at 100
Get 4.33 in calculator

.843x.885 is .746
4.33x.746 is is 3.23
Hths eq to 3.0 i get index of .93
Hths eq to 3.1 i get .96
Hths eq to 3.2 i get .99
Exact hths is unknown to me !

So i know it has low noack and little viscosity modifiers.
 
A couple I've done earlier
Supertech 5W30 (old data sheet) 0.895
TGMO 0.8465
Citgo 20W20 1.02
Ravenol 0W16 0.99
Castrol Edge 10W30 0.940
Castrol Edge A3/B4 5W30 0.9481
Castrol Edge 25W50 1.05
Hitec 10W40 0.946
 
Anything dexos 1 will work, but if I had a GM engine down here I wouldn't hesitate to run a quality 10w-30. They tend to have little VII and stand up to heat and shear very well
 
Pyb sae 30
Hths. harmon Index
3.0. 0.90
3.1. .93
3.2. .96
3.3. .99

Qsud 10w30
3.0 .92
3.1 .95
3.2 .98
3.3 1.01

Qsud 5w30
3.0. .95
3.1 .984

Pp 5w20
2.5 .93
2.6 .96
2.7 1.0

Does gm 4718m have min hths requirement
smile.gif

We know 5w30 and 10w30 above meet that spec.
 
Here are a few more.

Pp 5w30
Hths index
3.0 .90
3.1 .93
3.2 .96

M1 10w30
3.0 .933

M1 10w30ep
3.0 .93
3.1 .96

M1 10w30 hm
3.5 .926

M1 0w40
3.6 .87
 
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