Total and Component Friction in a Motored and Firing Engine, PhD thesis, 2004

[Jetronic]

https://etheses.whiterose.ac.uk/5354/

I have to read it properly soon, but was directed here from a reference in another white paper and it seems very promising. It compares measured friction losses between regular and friction modified oils, of differing SAE viscosity grades and at different realistic temperatures.

From the abstract:

A novel experimental system was developed to evaluate experimentally,
frictional losses in all the three main tribological components of an engine under fired
conditions.

They used a one cylinder engine as is expected for a research engine so I'll have to have a think how this compares to a 4 or more cylinder engine.

However it's past midnight right now and I really should go to bed, I suspect if I start on this it will keep me up all night.

 

[dnewton3]

Those are always interesting to read.

But at 20 years old, there's been a LOT of development in both the engine and oil technologies, as well as manufacturing processes. It's hard to know how much of that study is really relevant today in terms of conclusions drawn relative to today's ICEs and lubes.

 

[Jetronic]

I doubt physics changed that much.

I know now why the low viscosiy oils are chosen. They are not necessarily the best for fuel consumption in the real world, but they have an advantage below 60°c- ish) and under low load. The fuel consumption tests start with a cold engine in the EU, I presume it's the same in the uk, and loads on the engine are never high. That just favours the low viscosity oils. At operating temps, a 5W-30 is probably more economic than a 0W-20, in the 1500 to 2000 rpm region.

 

[JAG]

This looks like a very interesting paper. I will read it in-depth when time permits. Thanks!