UOA and repeatability of results

[harper]

People put a lot of stock into what a UOA states. How accurate/repeatable are the result?

I know this would cost twice the price, has anyone sent the same oil sample in twice over a short period to see repeatibility of results?

 

[Al]

There have been one or two comparisons in the past from this site as well as a discussion or two. Perhaps someone can dig up the comparison. You may find it by searching. As I recall out of 4 companies 3 were in the ball park and one had several results out there. I believe Blackstone was rated well here and in general I believe folks are very satisfied with their service. There is a member here Terry Dyson who works with Blackstone to interpret results. He is a top notch guy and if Blackstone is good enough for him its good enough for me.

 

[harper]

My engineering/scientific background coming out. Thanks for the reply.

 

[Pablo]

Harper - here's what I did earlier this year. NOT super scientific but almost better than nothing:

4 lab comparison

Not much study about repeatability has been done but there is some verbage on 3 mad pancho's (oil shoot out) site.

 

[YZF150]

Harper, see the VOA forum, too. G-Man had a bottle of Castrol 0w-30 tested twice due to an unexpectedly high iron count (9ppm). There was a significant discrepancy in the Calcium value between the two.

 

[CJH]

quote:

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Originally posted by harper:
People put a lot of stock into what a UOA states. How accurate/repeatable are the result?

I know this would cost twice the price, has anyone sent the same oil sample in twice over a short period to see repeatibility of results?

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Just wanted to say that differences in measuerments can be due not only to equipment variations but also due to the method of drawing the samples. The oil that you are drawing from is not completely homogenous throughout.

 

[Pablo]

As noted by YZ, Calcium and Phosphorous are notably all over the map. P is particularly hard to measure.

TBN (do a search) has been a majorbone.

 

[3 Mad Ponchos]

http://neptune.spacebears.com/cars/stories/margins.html

That includes a blind test as well as the ASTM reproducibility figures for the various tests.

http://neptune.spacebears.com/cars/stories/labtest.html

Pablo's test with some commentary.

Cheers, 3MP