Test Of Bearing And Oil Wear Rates - Conventional vs Synthetic

[LeoStrop]

Interesting test comparing wear differences using 5W20 Conventional vs 5W20 Synthetic.

https://www.chevyhardcore.com/tech-...gs-a-test-of-bearing-and-oil-wear-rates/

There is a couple of things that are "off", like the wear rates for Lead on the uncoated bearing + synthetic test, on the first chart (i think it should be the corect one) are 10ppm vs 23ppm on the second chart, it was also mentioned and changed the total metal count on both charts. The amount of zinc and phosphorus was also different on the same test compared to the other 3 that were the same.

 

[SonofJoe]

It's just my own personal opinion but it's testing like this that both blights & distorts the way people view engine oils.

It works like this...

Under 'normal' driving conditions, over the 'normal' life of a vehicle, using 'normal' commercial oils, with a 'normal' OCI regime, we..

(a) don't really see excessive bearing wear (& if we do, it's often a fault of bearing metallurgy or local over heating which has bugger all to do with the oil) and...

(b) we can't distinguish between conventional & synthetic oils in terms of bearing wear (and if you do, as often as not it can be ascribed to differences in the DI pack such as whether the ashless dispersant is capped or not or the presence of Moly).

HOWEVER...

If we put aside reality and frig the test & impose a combination of load/speed conditions that frankly would wreck an engine after 3 months, well under THOSE conditions, you can see a small difference & folks, THIS is why you should the best oils for your car.

I'm not picking on this particular report. This kind of thinking is pretty much ubiquitous throughout the industry. However when you superimpose one extreme test on top of another and another and another, you end up with a finished product that is massively over formulated & at the same time, ridiculously bent out of shape such that the oil's original purpose had been effectively lost.

 

[d00df00d]

Thanks, SonofJoe.

Questions about this:
Originally Posted by SonofJoe
(b) we can't distinguish between conventional & synthetic oils in terms of bearing wear (and if you do, as often as not it can be ascribed to differences in the DI pack such as whether the ashless dispersant is capped or not or the presence of Moly).

1. What does it mean for an ashless dispersant to be "capped"?

2. When you say we can't distinguish between conventional and synthetic oils in terms of bearing wear, are you assuming a short test on a clean engine where everything is at operating temp to begin with? I'd have thought that over the long run, with a normal amount of cold-start operation, the better cold properties and deposit control of a synthetic might net at least some small benefits in terms of bearing wear.

 

[SonofJoe]

Originally Posted by d00df00d
Thanks, SonofJoe.

Questions about this:
Originally Posted by SonofJoe
(b) we can't distinguish between conventional & synthetic oils in terms of bearing wear (and if you do, as often as not it can be ascribed to differences in the DI pack such as whether the ashless dispersant is capped or not or the presence of Moly).

1. What does it mean for an ashless dispersant to be "capped"?

2. When you say we can't distinguish between conventional and synthetic oils in terms of bearing wear, are you assuming a short test on a clean engine where everything is at operating temp to begin with? I'd have thought that over the long run, with a normal amount of cold-start operation, the better cold properties and deposit control of a synthetic might net at least some small benefits in terms of bearing wear.



1. Ashless dispersants have at their core something called a polyamine. Polyamines provide the polar nitrogen head groups that 'mop up' the crud in oil & hold it in suspension. So-called 'uncapped' dispersants are cheap to make & very effective. However they have a couple of unwanted side effects. First they are aggressive to nitrile rubber seal elastomers (causing them to crack). Second, they can react with the soft metal in bearings & pull it into the oil. It's not 'wear' in the traditional sense of the word but on a UOA, it would be indistinguishable from wear. The trick to solving both problems us to 'cap' the ashless by reacting it with an acid.

2. If you were comparing old-fashioned Group I conventionals to Group III/IV's, I might agree but in comparing Group II conventionals against synthetics, I wouldn't. The Group II oils which are ubiquitous in the US have oxidation resistance that's way closer to that of synthetics. They tend not to throw out that much crud. Regarding cold start, I assume in the interests of fairness, we would be comparing oils of similar viscosity grades (say a 5W20 conventional to a 5W20 synthetic) so this would be a moot point.

 

[alarmguy]

There is no difference in the wear rate of conventional and synthetic oil, they all meet the same standard.

 

[CT8]

Originally Posted by alarmguy
There is no difference in the wear rate of conventional and synthetic oil, they all meet the same standard.

We get so hung up with marketing claims that we forget what oil does and that is keeping the parts separated.