Originally Posted by Gokhan
(Image courtesy of 4WD)
In the past, they advertised the virtually VII-less 5W-20 as being thicker than a premium conventional 10W-40 loaded with VII.
It looks like not much has changed today:
M1 vanilla 5W-20:
HTHSV = 2.75
Base-oil viscosity = 1.91
VII content = 4.2%
M1 vanilla 5W-30:
HTHSV = 3.1
Base-oil viscosity = 1.77
VII content = 7.8%
M1 EP 0W-20 (PAO-based):
HTHSV = 2.7
Base-oil viscosity = 1.92
VII content = 3.8%
So, among the three M1 oils, the PAO-based M1 EP 0W-20 has the thickest base oil and least viscosity-index improver (VII). That's the power of the the high-viscosity-index PAO base oil. M1 5W-30 is the worst among the three as far as the base-oil viscosity and VII content is concerned.
The base-oil viscosity is probably more important than the HTHSV in TGDI engines or engines with fuel-dilution problems.
For example, see this Nissan paper on timing-chain wear. They compared a 0W-16 (HTHSV = 2.3 cP) to a 0W-20 (HTHSV = 2.6 cP) and found out that the timing-chain wear is controlled by the base-oil viscosity, not the HTHSV:
Development of low-viscosity API SN 0W-16 fuel-saving engine oil considering chain-wear performance
(Nissan study)
Excerpt: "Second, it was found that the base oil viscosity and molybdenum dithiocarbamate (MoDTC) had a significant effect on chain wear in rig testing that simulated silent chain wear. For the same base oil viscosity, the new oil maintains the same oil film thickness under high surface pressure."
PPPP 5W-30:
HTHSV = 3.1
Base-oil viscosity = 2.47
VII content = 2.3%
That's the power of GTL used wisely. The same doesn't hold for the Pennzoil Ultra Platinum (PUPPP).
PYB 5W-30:
HTHSV = 3.0
Base-oil viscosity = 1.82
VII content = 6.5%
The conventional Pennzoil 5W-30 outperforms the synthetic M1 5W-30 in base-oil viscosity and VII.
Estimated base-oil dynamic viscosit... improver (VII) content of selected oils
So, M1 5W-20 is fine unless your car really cares about the 10% higher HTHSV of M1 5W-30. It very likely doesn't.
If you need a thicker oil, go with the PPPP 5W-30. If you need something even thicker, go with an ACEA C3 5W-30 or something even thicker. Otherwise, there is no reason to worry.
^^^^^^^^^^^^
This validates in my mind what tig1 has stated. Many times in fact.. And that the need for new standard testing for viscosity came about. SAE J300...
His old school Mobil 1 was likely a legitimate 5w30... And performed great in his vehicles. Due to what gokhan makes clear here too.