Question about different labs, different test results

[Kennedy01]

I've been thinking about this for awhile. Earlier this year I sent an oil sample to Blackstone and it came back with much lower zddp additive concentrations than purported by the manufacturer and by a published independent report found online. I sent another sample to Oil Analyzers and that sample came back with concentrations matching both the manufacturer's claim and the independent test results. I emailed Blackstone about it and they said their lab equipment and results may differ from other labs. My question is why? I'm just trying to understand what would cause the discrepancy. Another additive level was off but I can't remember which one at the moment. I've read on this forum that it isn't uncommon for Blackstone to be off on certain additive concentrations.

 

[BigCahuna]

Alot of things in life don't match each other. Like if you bought gas in New Jersey and gas in California they probably won't test out exactly the same. Minorly different. Alot of items state + or - percentage wise, but both will run your car and not damage it. Even going between the same coffee shops and restaurants, will have items that don't look or taste exactly the same. Add the human factor into whatever is mass produced, and things won't come out exactly the same. Like that old saying, close enough for horseshoe's or hand grenades.,,,

 

[kschachn]

I've been thinking about this for awhile. Earlier this year I sent an oil sample to Blackstone and it came back with much lower zddp additive concentrations than purported by the manufacturer and by a published independent report found online. I sent another sample to Oil Analyzers and that sample came back with concentrations matching both the manufacturer's claim and the independent test results. I emailed Blackstone about it and they said their lab equipment and results may differ from other labs. My question is why? I'm just trying to understand what would cause the discrepancy. Another additive level was off but I can't remember which one at the moment. I've read on this forum that it isn't uncommon for Blackstone to be off on certain additive concentrations.

One thing That is important to understand right away is that you’re not measuring additive levels with a spectrographic analysis. For example you say “ZDDP level” but it’s not, all chemical compounds are decomposed in the plasma and you’re only reading elements. So sometimes it has to do with the operation of the machine and making sure that all elements are completely decomposed.

Proper calibration of the ICP machine is critical to accurate results. Sometimes these calibration routines are lengthy and complicated, there was a post here at one time which noted that for an ICP machine it takes about an hour. You also have to spend money on calibration reagents that are expensive.

There are also different ASTM or ISO test routines and sometimes the different routines do not produce identical results. You always have to make sure that you are comparing apples to apples. These test procedures must be followed to the letter in order to obtain the repeatability and reproducibility values that are listed in the routine. If you deviate in any way there’s no telling what you’re going to end up with.

 

[Astro14]

I've been thinking about this for awhile. Earlier this year I sent an oil sample to Blackstone and it came back with much lower zddp additive concentrations than purported by the manufacturer and by a published independent report found online. I sent another sample to Oil Analyzers and that sample came back with concentrations matching both the manufacturer's claim and the independent test results. I emailed Blackstone about it and they said their lab equipment and results may differ from other labs. My question is why? I'm just trying to understand what would cause the discrepancy. Another additive level was off but I can't remember which one at the moment. I've read on this forum that it isn't uncommon for Blackstone to be off on certain additive concentrations.

I’ve used this analogy before...hoping it helps.

Chemical compounds and their performance are like text on a page. Some people write well. Some don’t. Some words are good. Some aren’t.

Ultimately, what you care about is effectiveness of the writing.

Spectrographic analysis measures how many letters of each kind are in the writing. It‘s measuring elements, not compounds. Not how those compounds perform.

Knowing how many of each letter tells you…how many letters were used.

Not what words were used. Not how those words worked together to make good writing.

So, you’ve inferred performance by measuring relative concentrations of elements. That’s no more accurate than deciding how clear your post was by measuring how many times you used the letters, “r, s, t, l, n, e”.

 

[Kennedy01]

Ok I understand. I didn't mean to infer that a product's performance is based solely on additive concentrations. I was more wondering about what factors can dictate a difference in the numbers you see on an analysis. You guys described it well. There was just such a departure between one labs results and another that it seemed like something wasn't right. Ppm differences we're as much as 300 ppm on both the zinc and phosphorus element numbers between Blackstones sample and Oil Analyzers sample. But again I know those numbers aren't the bulk of the products performance. Thanks for taking the time to explain.