On my last 5 Blackstone UOA reports the water %s were all reported as "0.0". This is based on driving sporadically about 4k+ miles over a year with one annual oil change. Car is currently having it s oil changed now, will report next UOA in about a month.
Is this the type of data point you are looking for?

 

Understood and thanks for the explanation. You raise valid questions. Here is another possible scientific justification. These cars are prone to fuel dilution from leaking injectors. The “experts” mentioned recommend new injectors at 60,000 -80,000 miles on the M96-M97 because of this. Gas is a solvent. Leaking direct injectors wash all the lubrication off the piston skirts and cylinder sleeves. This quickly leads to bore scoring in the cylinder with the leak. Bore scoring = $20k engine rebuild/replace. So, it is critical to monitor the fuel dilution in your oil to catch and correct a leaking injector as soon as it occurs. The best method to do this is with a semiannual used oil analysis. That means a six month oil change interval regardless of low miles. Now, I personally have no issue with stretching that OCI out from 6 to 12 months if the mileage driven is below threshold. Just voicing another possible justification for frequent oil changes on the M96/97 engines.

Here is another argument that is practical. Those oil experts over at the “Bob IS The Oil Guy” website insist that oil has a shelf life. While they argue about exactly what it is, they generally agree it is somewhere between 2 and 4 years. So, those of us who buy oil in bulk when on sale should be recording the dates on the cases and change oil as often as needed to consume inventory every two - three years…..or just quit buying it in bulk when on sale. Haha. Why throw away good, unused oil that is close to expiring. With regular maintenance on four vehicles, I buy lotsa oil.

And my final point is this………I just like going to my garage, turning up the radio, cracking a beer and changing my oil. So, I do it more often. My version of golf!

Happy holidays to All!

 

Yes, amongst others. Water, fuel dilution, flashpoint, TAN, TBN, Al, etc. Looking for accumulating water and fuel (the "percents"), then the effects of any accumulated water and fuel (wear metals (elevation brought on by acidic environment), TAN, TBN, flashpoint, etc.).

 

I think what he's looking for is a TAN / TBN analysis that's shows a low mileage but long time UOA where the TAN is unusually high or metal wear has increased beyond the history of higher mileage oil changes in this lower mileage, longer time one. I think it's been a while since I changed my wife's 997 oil since she doesn't drive it very often (takes my truck for yardwork and why I bought another 928 to be my DD).

So may have just the report you're looking for at her next oil change - might be over a year, coming up on 2, but under 3k miles.

 

Excellent suggestion to use the OCI to catch a particularly bad problem for this engine.

Regarding excess fuel, does anyone know/studied what kind of drive (ambient conditions, duration, engine oil temp, etc.) drives off (boils out) the fuel? For example, a typical leaking single injector might add 2 ml to the crankcase and a 32 minute typical "grandpa" (no offense intended) drive evaporates 99pct of the crankcase fuel. There might also be a thermodynamic approach that can estimate it.

 

And how would you characterize the drives that it did have? - longer with conditions to get rid of the water and fuel, or, shorter with not much opportunity to drive off water and fuel?

 

Nothing longer than probably 30 minutes with most being 10 minutes (home to gym, home to school to pick up our son, school to the golf course, a hook to the guitar studio....lots of small short drives with every 20th or 30th being a longer one.

 

Thanks Pete. I think your usage/UOA will be a great counter-example to the conditions I originally offered. Since I know you take excellent care of your vehicles (your posts testify that you are a mechanic's mechanic) your data will be very valuable.

 

I will post my next UOA in the next month or so- it will have all the info (TAN/TBN etc) you are requesting over six oil changes and the type of usage, wear metals and OCI you are referencing.

 

Mental masturbation. Change it once a year and youll be fine

 

The evidence comes from more than UOA, it comes from direct experience dissembling failed M9X engines for the last 18 years. I never recommend this interval to people that don't have my engines, but for those owners, it is a mandate. Anyone else can do whatever they want.

 

I changed my oil recently. I only went 1300 miles in about the 2 years between the oil changes (so sad). I had the used oil analyzed at SPEEDiagnostix. Attached are the results.