My usual source for parts stocks two "synthetic" oils that meet the MB 235.8 spec. So, I was considering these two different 75W-90 differential gear oils. My brother and I got to discussing the practical implications of different oil compositions that meet the same specs.
So, I'm just using these as an example with very similar specs but different base stock; I'm not trying to pick on either.
The Red Line is a "full synthetic" while the Liqui Moly is "semi synthetic" blended with Group III base stock (Based on manufacturer claims and SDS sheets).
The numeric specification differences seem negligible. In a case like this, what is the real gain / practical implication of choosing one over the other? What would be a "defensible" reason to choose one or the other when they both meet the specification I need to meet?
I'm more generally interested than this specific scenario, it just seemed like a good example to use.
[After starting this conversation, I went looking at other options that are 75W90 and meet MB 235.8 as well. Specifically, I found Mobil 1 Delvac 75W90 (blend) to have a measurably lower viscosity index than these two, and Ravenol VSG 75W90 (full synthetic) to have a higher viscosity index than all of them. That said, I'm still not sure what motivates someone to choose one or another when they all list the same specifications.]
So, I'm just using these as an example with very similar specs but different base stock; I'm not trying to pick on either.
| Liqui Moly 75W90 GL4/5 | Red Line 75W90 GL5 | |
| Part Number (1qt) | 22090 | 57904 |
| Viscosity @ 100°C (cSt) | 15.6 | 16.1 |
| Viscosity @ 40°C (cSt) | 106 | 108 |
| Viscosity Index | 157 | 161 |
| Pour Point (°C) | -51 | -45 |
The Red Line is a "full synthetic" while the Liqui Moly is "semi synthetic" blended with Group III base stock (Based on manufacturer claims and SDS sheets).
The numeric specification differences seem negligible. In a case like this, what is the real gain / practical implication of choosing one over the other? What would be a "defensible" reason to choose one or the other when they both meet the specification I need to meet?
I'm more generally interested than this specific scenario, it just seemed like a good example to use.
[After starting this conversation, I went looking at other options that are 75W90 and meet MB 235.8 as well. Specifically, I found Mobil 1 Delvac 75W90 (blend) to have a measurably lower viscosity index than these two, and Ravenol VSG 75W90 (full synthetic) to have a higher viscosity index than all of them. That said, I'm still not sure what motivates someone to choose one or another when they all list the same specifications.]
