I've pretty much mentioned pump slip in many of these discussions, and I've never said every PD oil pump is perfect or never wear out. Like I said, there are many factors usually involved in these not so straight forward root causes scenario discussions. Re: your bolded statement ... basically what I said, guess you agree.
Yup, that seems like a strawman being erected just so it could be knocked down.
I wouldn't say pumps have "all kinds of problems", but they do wear, and, in some applications, like GM ones, they can suck air due to failing o-rings. There are also a number of different pump designs, which is going to have an impact on wear, bypass...etc.
I'd also like to know what "slightly lower than normal" oil pressure is.
In the context of the HEMI specifically:
The ECM infers viscosity from oil temperature and pressure. This is done for proper MDS and VCT operation; it's basically a "knowledge" factor for the ECM so it knows what to expect. There's clearly some liberal fudge factor involved to allow for shear, fuel dilution and oil to oil variance, because people have been able to run 30 and even 40 grade oils in the 5.7L and it takes a bit of effort to get it to throw the "wrong viscosity" code. User Clevy had it happen in his Charger R/T with 0w-40 when it was like -40C.
However, that's the upper end of the spectrum, I don't know what the bottom looks like; what it considers the floor for acceptable oil pressure at a given oil temperature and that may be what has resulted in this TSB. The oil pressure is measured AFTER the filter, so if the filter is plugging up and pressure drop across the media is significant to the point where the bypass is being employed at idle, well, if that's a 15psi differential pressure and feed pressure on the pump side is 30psi that gives us 15psi on the side the ECM is reading and that could be enough to trigger a CEL or a "WTH" reaction when reading the gauge. Of course the pump not being on the relief, the same volume of oil is being shuffled, so it's not going to hurt the engine, but it could definitely trigger a code.
On soot, well, port injected engines don't typically generate much in the way of soot and soot particulate is typically small enough to pass through a filter unless it is significantly agglomerating. If this was a DI engine (some of the GM ones in question are) then yeah, I suppose soot agglomeration could be a factor, but with the HEMI, which has never been DI, it would be much less of one. It is however a "dirty" engine by virtue of its combustion chamber design and tends to produce particulate that's large enough to end up in the filter.
An interesting article on DI soot can be found here:
In this work, an investigation of soot-in-oil samples drawn from the oil sump of a gasoline direct injection (GDI) engine was carried out. Soot partic…
www.sciencedirect.com
You'll note that the average soot particle is 36nm, which is 0.036 microns according to this calculator:
Instant free online tool for nanometer to micron conversion or vice versa. The nanometer [nm] to micron [µ] conversion table and conversion steps are also listed. Also, explore tools to convert nanometer or micron to other length units or learn more about length conversions.
www.unitconverters.net
Since we are talking about filters with high efficiency figures between 15 and 20 microns, clearly DI soot particles aren't plugging filters unless they are agglomerating significantly more than found in that study, which showed a mean length of 153nm and the range extended to 405nm (.4 microns):
The mean skeleton length, LSk and width, WSk were found to be 153 nm and 59 nm, respectively. 66% of the agglomerates presented a skeleton length between 90 nm and 180 nm, with LSk ranging from 53 nm to 405 nm. Long agglomerates with skeleton lengths longer than 300 nm accounted for 9% of the agglomerates. The skeleton width spanned from 33 nm to 102 nm, with 70% of agglomerates in the range 60–80 nm.
Quoting more of the article:
The
particle number concentration emitted by GDI engines are generally higher than conventional PFI engines and
Diesel engines equipped with Particulate Filter (DPF). Most of the soot produced is expelled from the cylinder with the exhaust gases but a small proportion is transferred from the cylinder to the
lubricating oil. Soot is likely to migrate into the oil film early during the expansion stroke
[8]; consequently, the morphology, agglomeration and other characteristics of soot-in-oil are likely to be rather different to exhaust soot. Soot-in-oil has not been subject to oxidation processes to the same extent and hence the outer
shell structure is more likely to remain intact. Although only a small proportion of the soot formed in the
combustion chamber transfers to the engine oil, it contributes to the
lubricant degradation. This is certainly a new challenge for the modern GDI engine as soot-in-oil raises concerns upon wear and
engine durability.
Now, since the GM engines also have cylinder deactivation and camshaft phasing, they too could be inferring viscosity from oil pressure and thus experiencing the same sort of issue, but I've not researched that.
Ultimately, it sounds like some of these engines just shouldn't be running extended drains with high efficiency filters.
Per
@Greasymechtech's query about larger filters, yes, the SRT's spec the larger XG2 (FL-820S) filter (the same filter the older 5.7's spec'd) and it can fit on many of the 5.7's still, though it is tight. I run one on our DT.