Originally Posted By: dparm
Trying to make absolutely certain I understand this correctly.
Oils with large viscosity spreads (5w50, for example) require very good basestocks and/or VIIs. And in general, those VIIs will lead to shearing under extreme conditions, such as sustained WOT. This is because the VIIs breakdown under load.
Conversely, oils with small viscosity spreads (5w20, for example) do not require as good of a basestock and/or fewer VIIs. Since there is less reliance on VIIs, the oil is generally more shear stable.
Correct?
Trying to get clarity as the weather warms here and racing season begins for my DD. Thinking a move to 10w40 might be more prudent now, and leave the 5w30/5w40 for the winter. HTHS is a very important number for racing conditions, but shearing is still a concern.
The 10w40 I am considering has a slightly lower HTHS and VI than the 5w40 (4.19 vs 4.51, and 161 vs 196, respectively), but I would assume it is much more shear stable oil and better suited to racing.
The viscosity-index improver (VII), viscosity index (VI) of the base oil, and A_Harman index are back!
Below is a table for some A_Harman indexes I calculated. Note that A_Harman index
only measures the temporary high-shear-viscosity loss resulting from the temporary VII shear (in high shear regions of the engine such as the bearings) and
not the permanent viscosity loss from permanent VII shear and/or total VII content (unsheared + temporarily sheared + permanently sheared).
In summary, PAO and GTL do best in the A_Harman index.
For your racing application, I recommend Pennzoil Platinum Euro with PurePlus 5W-40. It should have a good A_Harman index and a high HTHSV. Of course, you can always upgrade to Amsoil if you like.
A_Harman index = HTHSV / (KV150 * density @ 15 C * 0.885)
(KV150 is extrapolated using the
Widman operational-viscosity calculator or such. The factor 0.885 is for the density extrapolation.)
Here is the
Excel file (link) for the table.
Code:
Oil Density KV40 KV100 KV150 HTHSV VI DV150 A_Harman index
Delvac 15W-40 CK-4/SN 0.874 109.00 14.10 5.32 4.10 4.11 0.996
M1 AP 5W-20 0.850 48.88 8.20 3.53 2.60 141 2.66 0.979
PPPP 10W-30 0.841 60.50 10.10 4.29 3.10 151 3.19 0.971
M1 HM 5W-20 0.856 50.00 8.60 3.72 2.70 150 2.82 0.958
Shell Rotella T4 15W-40 0.878 113.72 14.84 5.68 4.20 4.41 0.952
M1 EP 0W-20 0.839 44.90 8.60 3.85 2.70 173 2.86 0.944
PPPP 5W-30 dexos1 Gen 2 0.839 53.90 9.80 4.28 3.00 170 3.18 0.944
PPPP 5W-30 0.839 53.90 9.80 4.28 3.00 170 3.18 0.944
M1 5W-20 0.852 49.80 8.90 3.89 2.75 160 2.93 0.938
M1 EP 5W-20 0.850 49.60 8.90 3.90 2.75 161 2.93 0.937
Amsoil SS 5W-30 0.855 59.70 10.30 4.41 3.11 3.34 0.932
M1 0W-20 0.841 44.80 8.70 3.91 2.70 177 2.91 0.928
M1 HM 10W-30 0.861 78.00 12.10 4.96 3.50 3.78 0.926
Amsoil XL 5W-30 0.855 62.90 11.10 4.77 3.30 3.61 0.914
M1 AP 0W-20 0.840 45.69 8.70 3.89 2.60 172 2.89 0.899
PUPPP 5W-30 0.841 56.30 10.30 4.50 3.00 173 3.35 0.896
M1 EP 5W-30 0.851 59.80 10.60 4.57 3.00 169 3.44 0.872
Pennzoil HM 10W-30 0.871 78.80 11.80 4.79 3.20 144 3.69 0.867
M1 FS 0W-40 0.846 70.80 12.90 5.56 3.60 185 4.16 0.865
Rotella T6 5W-40 CJ-4 0.858 86.94 14.09 5.80 3.80 4.40 0.863
M1 5W-30 0.855 61.70 11.00 4.75 3.10 172 3.59 0.862
M1 ESP Formula 0W-40 0.841 69.00 12.90 5.61 3.53 191 4.18 0.845
TGMO 0W-20 SN MSDS 0.851 36.10 8.50 4.09 2.60 225 3.08 0.844
M1 AP 5W-30 0.851 67.52 11.24 4.74 3.00 160 3.57 0.840
TGMO 0W-20 SN VOA 0.851 36.16 8.79 4.27 2.60 236 3.22 0.808
M1 HM 10W-40 0.860 107.00 16.00 6.37 3.90 4.85 0.804
M1 HM 5W-30 0.856 72.00 12.10 5.09 3.10 151 3.86 0.804
M1 HM 5W-30 0.856 72.00 12.10 5.09 3.10 166 3.86 0.804