the Impact of Lubricating Oils on Friction/Economy

[Shannow]

"Research on the Impact of Lubricating Oils on Engine Friction and Vehicle Fuel Economy"

http://www.atlantis-press.com/php/download_paper.php?id=25837920

Chinese paper on their push for better utilisation of fuels.

Warning, it has a couple of Stribeck curves in it. Obtained from motored engine friction tests.

Also, for the peanut gallery regarding those motored engine tests.

Power (Watts) = Revs per second X 2*Pi (converst RPS to radian per second) * torque (Nm).

That's how much heat is being generated in the shearing of the oil between moving surfaces.

 

[beanoil]

More data to back up common knowledge that thin oils increase fuel economy. What special elf sweat did they find was the best FM though?

 

[Shannow]

Having a paper with multiple motored engine tests on multiple viscosities, at multiple temperatures was pretty flash I thought. I've seen a couple of papers with motored tests, but never that.

The low speed mixed lubrication stepping up to the impact of full on hydrodynamic lubrication at speed was also good.

If you want to break it don to "thin oil saves fuel", have at it, but the stuff in the paper was interesting.

And yeah, wonder what their FM was.

 

[Lex94]

Thanks Shannow!

Can you explain it to me since I'm too lame to load it and Chinese math sucks....

 

[Shannow]

Lex94,
here's one that's an easier read.
http://cdn.intechopen.com/pdfs/44506.pdf

Shows bearing temperature rises with viscosity and RPM.

At the end, there's a chart that demonstrates the push for higher VI/Lower viscosity lubricants, showing the total bearing power drain for a variety of RPM, for a couple of different oil grades. the "mm" reference is bearing width.

That's why I keep the revs up in town on my morning commute, holding about 2,500-3,000RPM rather than 1,500-2,000...more heat generation in the oil leads to a notably faster warm-up.

 

[DriveHard]

Doesn't this mean that a higher viscosity oil would warm up faster? I have often seen it mentioned that it is this time spent between cold and hot oil is where the most wear occurs. The oil has thinned enough to allow metal to metal contact, but the additive package is not yet activated. Since the difference is so low at normal operating conditions, doesn't it make sense to go with the thicker oil for much quicker warm up and reduced wear associated with that? Most cars cruise at 2000 to 3000 max on the highway, and there is less than a quarter of a kw at the worst case...and pretty much negligible near 2000 where most cars cruise. What % of power required is that to cruise a car down the road? From the link below a Crown Vic (site fave) takes between 11kw and 15 kw to maintain 60 to 65mph. So at most it is a 1.5 to 2% increase in efficiency...if your car cruises at 3000 rpm.

If thick oil warms faster...thereby protecting the engine better, does it still make sense?