Date registered: Feb 2007
Vehicle: 03 E320 4M Wagon & 97 E320
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Quoted: 12 Post(s)
Although oil consumption (burning off) is kind of related to oil viscosity at 100 deg C, there are other important factors to consider.
The short answer is that an engine will consume less Mobil 1 5W-40 than 0W-40, if all other things are the same. Here are the factors:
1) Even though both are xW-40 oils, a 5W-40 tends to be a little thick than 0W-40 at 100 deg C. For example, 5W-40 has 14.8 cSt and 0W-40 has 14.3 cSt at 100 deg C, a difference of 3.5%.
2) The 0W-40 has to start with a thinner base stock. More viscosity improver and other additives are needed to raise the viscosity at 100 deg C at the 5W-40 level. Because it is a thinner base stock, it will consume more when the additives wear down a bit.
3) The more important spec is the High Temperature High Shear (HTHS). This is measured at 150 deg C so it is better suited to judge oil consumption. 5W-40 has an HTHS of 4.1 while 0W-40 has only 3.6. That is a difference of 14%.
4) Finally the best spec to judge this is the NOAK volatility. However, Mobil 1 does not release this number. Amsoil et al often tests this to show how their oils are superior in this department than Mobil 1.
On a related note. That is why the HDEO 15W-40 oils are so stable and engines will consume less of it than say, 10W-40.