2016 BMW 535i w/ N55 engine @ 56k miles; QS Euro 5w-40 5.5k miles

[BMWTurboDzl]

The flash point is what’s used to infer fuel dilution.

And we have seen Blackstone estimates that are way worse than 0.013 discrepant. More like several percentage points.

I wasn’t even looking at the flashpoint. Just the fuel number itself.

I’m acutely aware of the costs and challenges associated with high fidelity analytical equipment. And the RSD that is appropriate.

That said, absolute accuracy or consistency isn’t the whole name of the game. The right tool and the right fidelity at the right place and time is necessary. I don’t need to know if it’s 0.5 or 0.513%. I need to know if it’s varying by percentages.

Per BS there error rate on measuring flashpoint isn't very high.

"Based on the margin of error for the methodology we use for measuring the flashpoint, the lowest fuel dilution value you’ll see on one of our reports is <0.5%. That’s our way of essentially saying that no measurable fuel dilution was detected in the oil. If the flashpoint of your sample reads the same as the “should be” value, we’ll report a “TR” (or trace) of fuel dilution. In other words, it’s likely there was a very small amount of fuel dilution present, but not enough to quantify. After that, you’ll see fuel dilution reported as a percentage of the sample. The most fuel our test can accurately read is 10%. If you have more than that, we’ll report >10% (and you should head to a mechanic)."

What is a Flash Point? | Blackstone Laboratories

www.blackstone-labs.com

 

[kschachn]

The "error rate" on measuring flash point is given in the test itself. Blackstone can do no better than that.

It's inaccurate. We have seen UOA on here multiple times where the flash point inferred value is far lower than a direct measurement. Search around for specifics but there are instances where Blackstone reports less than 0.5% while another lab says it is greater than 5% using GC.

 

[JHZR2]

The flash point is what’s used to infer fuel dilution.

And we have seen Blackstone estimates that are way worse than 0.013 discrepant. More like several percentage points.

Well 0.013 was just a made up number to make a point. Either it’s there or not. I was under the impression they had performed a test that was more specific, not just an attempt at a correlation…

Thanks for clarifying that.

 

[BMWTurboDzl]

The "error rate" on measuring flash point is given in the test itself. Blackstone can do no better than that.

It's inaccurate. We have seen UOA on here multiple times where the flash point inferred value is far lower than a direct measurement. Search around for specifics but there are instances where Blackstone reports less than 0.5% while another lab says it is greater than 5% using GC.

How do we know the variance is a result of the test rather than operator error? Answer: We don't.

 

[kschachn]

How do we know the variance is a result of the test rather than operator error? Answer: We don't.

Yes of course. Blackstone could be repeatedly incompetent, but like you note we don't know that. So I chose not to be inflammatory.

 

[BMWTurboDzl]

You don't know anything about standardized tests, do you?

Not enough but standardized tests don't prevent typos

 

[kschachn]

Not enough but standardized tests don't prevent typos

So Blackstone makes typos? That’s the reason?

 

[himemsys]

I have one data point comparing BS to OA fuel dilution. BS said <0.5% using the inferred method from the flashpoint. OA (using gas chromatography), measured 1.7% on the same oil sample. That's over 3x difference. I've seen others that show a wider discrepancy.

 

[ps2cho]

First, I don't have a lot of faith in BS viscosity measurements. They always seem to come in low and then go up once retested.
Second typical 40 grade euro oils are on the low end of the viscosity range for that grade to begin with and there's going to be some movement through the OCI.

Your oil is good for 10k miles.

Sounds good - I'll split the difference and go for an 8k change interval next and retest and see if theres any notable difference.

 

[BMWTurboDzl]

So Blackstone makes typos? That’s the reason?

I have one data point comparing BS to OA fuel dilution. BS said <0.5% using the inferred method from the flashpoint. OA (using gas chromatography), measured 1.7% on the same oil sample. That's over 3x difference. I've seen others that show a wider discrepancy.

GC can provide an error of up to 2% in some circumstances.

"Getting the best result using GC analysis can be very time consuming since there are cases in which there is overlap in boiling points between fuel and certain engine oil formulations. These overlaps can introduce errors of up to 2% fuel dilution if left unchecked. In these cases, the temperature, pressure, or column may need to be optimized for the specific oil type. Many commercial laboratories have modified the traditional ASTM methods in favor of a faster and more robust method developed by a leading GC manufacturer.7"

https://www.spectrosci.com/en/knowledge-center/test-parameters/measuring-fuel-dilution-in-lubricating-oil#:~:text=The%20repeatability%20is%20%3C5%25%20RSD,minimum%200.2%25%20fuel%20dilution).

 

[edyvw]

There is NOTHING to worry about this oil!

 

[vinu_neuro]

Yea I'm surprised to see so much discussion around the viscosity. Regardless of engine and oil brand, the euro 40wt oils fall below 12st pretty quickly. They've always had some initial shear almost immediately and there's some fuel dilution with almost every gdi engine today.

 

[edyvw]

Yea I'm surprised to see so much discussion around the viscosity. Regardless of engine and oil brand, the euro 40wt oils fall below 12st pretty quickly. They've always had some initial shear almost immediately and there's some fuel dilution with almost every gdi engine today.

QS 5W40 starts very thin 40. Some VOA shows as thick 30.

 

[vinu_neuro]

QS 5W40 starts very thin 40. Some VOA shows as thick 30.

They're all below 12cst after a couple thousand miles, it's the same story with M1 and Castrol 0W-40, and the 5W-40's. One has to assume that range is the design target operating viscosity for most of these oil manufacturers given the prevalence (and presumably the engine manufacturers since the big name oils and developed in partnership with engine OEM's).

 

[edyvw]

They're all below 12cst after a couple thousand miles, it's the same story with M1 and Castrol 0W-40, and the 5W-40's. One has to assume that range is the design target operating viscosity for most of these oil manufacturers given the prevalence (and presumably the engine manufacturers since the big name oils and developed in partnership with engine OEM's).

Depends on the engine, driving style etc. I had Mobil1 0W40 and Castrol 0W40 staying within grade in known fuel diluters.
Too many variables. This is good report.