I'm a proponent of the 5K max miles between changes. But all of the 997.2 Blackstone analysis I've done (limited data, I'll admit) come back with the statement that longer durations are advised. FWIW I'm sticking with 5K.

 

The secret to the Blackstone analysis is knowing how to read the actual numbers and data and pretty much ignoring the comments in the top section. They are some of the most positive outlook people I've encountered and I see things in the analysis that they have either glossed over or missed.

Here's a perfect example. From the numbers, this oil was run too long. Flashpoint is too low and with a TBN number of only 3.2, the TAN number (which they forgot to run in this sample) would probably be closer to 5 or 6, so the oil is more acidic than basic - that's bad. Yet, in the comments, they say that things look good and I could shoot for an even longer change interval of 8,000 miles next time.

In every UOA I've done on any vehicle - Porsches, boat, pickup, Japanese SUV, etc I see significant degradation in the oil anywhere from 4,000 miles to 5,500 miles. I use the uOA to determine the proper change interval for that specific oil in that particular car. I never want to see double digit wear metals of any type, viscosity needs to be above the minimum, both Zinc & Phosphorous levels need to be above 1,000 ppm (for the oils I run) or maybe just a hair below if the other numbers look good), low or no fuel dilution, no anti-freeze presence, and a TBN number that's higher than the TAN number. If an UOA fails any of these benchmarks, I lower the oil change mileage interval until they're all where I want them to be. Based on my experience, no one should run any oil longer than 5,000 miles, and in some cases, even that's too long.

I don't know what oil was in this car when I bought it, but that's the change that was at 28k miles. The one below is Driven DT40, but the first oil change with it, so not representative of future ones.



Here's another example where the oil was run too long, so even 5,000 miles on this oil in this car is too long - TAN exceeds TBN and flashpoint is still low. I'll be moving this car to a 4,000 mile interval and seeing what that UAO looks like, specifically looking for a better flashpoint and lower fuel dilution. Since my AFR #s when driving the car are good, if I still see a fuel dilution trend, I'll replace all the injectors. That's exactly what doing this type of UOA is used for - to catch potential issues as they're developing before they become major issues and cause major engine damage.

But, see, the comments on this report is still pretty positive, even though I don't particularly like these results.

 

Great info to summarize all in one place. Thanks ... Wayne

 

Thank you all for the responses.

 

I'll bite. I bought my car and was concerned initially about a scored bore. There was a concerning sound that sounded like every scored bore I'd ever heard online. I had it scoped above/below - no score. I have noticed slightly uneven sooting on sides since I've had it. I've now had 2 Speediagnostix oil analyses done, changing the oil every 5k (3rd coming up in 1k miles) and both have been totally clean for abnormal wear particles. YMMV but perhaps start with an oil analysis? Hard to believe I will have put 15k miles on my car in 1 year of ownership.

 

My 24k miles 09 4S. Left tips are always a bit dirtier than the right ones.

 

It has something to do with condensation in the exhaust mixing with soot, as I see some small little droplets on my bumper mainly on the left side of the car, left side exhaust tips are slightly darker than the right side. But it does pretty much disappear during Summer and into the season running. 24k miles 09 c2s.

See above photo for lhs floor markings

 

This brings up the question ... Does one side develop more condensation than the other?

This could explain the preponderance for the heavier soot on the left side that seems to be almost universal in the .2 cars from what I've observed.

I don't see why one side would be different but maybe someone else does.

 

Wow

 

Forgot to say that the sound ended up being a noisy high pressure fuel pump