Can UOA miss a bad engine condition?

[NismoNVT]

Came across a oil consuming corolla

The engine had crazy blow by, beat up rod bearings causing a knock on startup, and burned tons of oil. Overall, the motor was in very very bad shape. I expected metal shavings and lots of other crap in the oil. They got an oill analysis back that read normal, with everything measured at or below averages, except for a higher viscosity from some Lucas that had been added. Recommended to run 5k more on that oil. When tearing it down for rod bearings were thoroughly chewed up.

Is a single UOA unable to determine such wear?

 

[buster]

Yes because a UOA only measures a very limited particle size (5 to 8 microns).

 

[RDY4WAR]

ICP only looks at particles 10 um swimming around in the oil, they won't show up on UOA. A UOA will usually not tell you about a sudden, catastrophic failure. It's to observe trends over repeated oil changes to look for signs of excessive wear occurring. It's also possible for a high efficiency filter (particularly a bypass filter) to capture a lot of particles out of the oil, leaving little to show in the sample.

 

[Brian123]

Used Oil Analysis - Bob is the Oil Guy

UOAs are a great tool in the Management of any machinery that uses liquid lubricants. Unfortunately, their real value is often misunderstood by those who contribute to BITOG. Firstly, it is important to realize that you get what you pay for. The most common forms of UOA are limited in their...

bobistheoilguy.com

There is a section on this Forum that explains everything or most of it about Used Oil Analysis

 

[kschachn]

Singular UOA are limited. When I ran oil analysis in college without an acid digestion of the sample particles are not typically measured. As explained in the posts I link here the ICP is not a particle measurement device.

Might the use of magnets affect oil analysis results?

I was reading a thread about the use of drain plug and oil canister magnets, and my thoughts gravitated towards oil analysis results. If one is using strong magnets that pull iron from the oil, might that skew the Fe ppm in an oil analysis, showing less iron in the oil as more is collected by...

bobistheoilguy.com

 

[jeepman3071]

UOAs are great for determining the condition of the oil, which can give hints on the condition of the engine, but isn't an accurate way to diagnose anything. The BMW M car guys seem to use UOAs to check for rod bearing wear, but it isn't always a good indicator. I'd be willing to bet that in those cars you'll hear a rod knock before you see bearing materials elevated enough to cause concern. A UOA gives a snapshot of how the engine is wearing over a given mileage interval, not how worn it is in general.

 

[edyvw]

Used OIL analysis. NOT Used ENGINE analysis.