These DI oil threads have me thinking this:
There, in the last 6-7 years, has been a massive increase in the production and sales of vehicles with Gasoline Fueled Direct Injection engines. This will continue to increase.
There are three issues, in general, with these engines. These are issues that, in general, did not apply to non DI engines for the previous 20 years.
1. Soot- DI engines produce soot, much like a diesel. This soot goes out the exhaust, which means the probable advent of GPF. However, for our purposes, soot also becomes entrained in the oil. The main drawback to these particles being in the oil, is that it greatly increases timing chain wear. Seems to apply to all DI engines.
2. LSPI- Real issue. Seems to affect some engine designs more than other.
3. Fuel Dilution- Real issue. Seems, again, to depend on engine design, and driving conditions.
So, for the previous generation of engines, a "conventional wisdom" grew up, of "extended" oil changes, "synthetic" oil is better than "conventional" oil, tribologic film, etc. For the previous generation of engines, this probably worked pretty well. If you have a previous generation engine, keep on keepin' on
If you have a new DI engine,it is a whole new game, because of the three previously mentioned issues.
"Extended" oil changes on DI are not good. Soot accumulation and fuel dilution rule this out. You say your UOA wear levels are good? Does a UOA measure how soot levels are affecting your timing chain?
Tribologic film, you say? The fuel dilution literally changes your oil. It is not the same oil as when it was new. Fuel dilution(particularly ethanol blended gasoline) reduces(or eliminates) your boundary layer lubrication. It also reduces your viscosity, and essentially your oil becomes a oil/gasoline/ethanol blend. So, if you're saving your tribologic film for your next oil change, forget it. You don't want that one.
There is some evidence that the more used your oil is(as opposed to new or newer oil), that influences LSPI negatively. Thin oil, you say? There is some evidence that lower viscosity affects LSPI negatively. Synthetic oil, you say? There is some evidence for Group I-IV oils, the higher the Group, the more LSPI. These three are all secondary, or tertiary, but still evident.
One overwhelming fact in the evidence, so far, is that the detergent metal Calcium, in commonly used compounds, greatly increases the incident of LSPI, particularly above 1500 ppm. The addition of a detergent Sodium metal compound(again, any commonly used compound) to the Calcium, greatly increases LSPI incidents. Detergent Magnesium metal compounds are LSPI neutral. Molybdenum compounds DECREASE LSPI incidents.
The auto manufacturers are pushing SAE and ILSAC hard to come out with new standards, fast, that they can back spec to the earlier DI engines. This is probably so they won't have to come out and say the oil you are running now, in your DI, is not the best. If you think this is some kind of money grab by some entity in the industry, then you will probably continue to think that. These new standards are to address the above issues. So, the advice of "Just follow what the owner's manual says", may not always be the best advice, for a DI engine user.
The point to this?
If you have a previous generation engine and want to provide advice to someone with a previous generation engine, go for it. But your advice for a previous generation engine, provided to a DI engine user, is coming from a place of misplaced wisdom.
There are probably tens(hundreds?)of millions of DI engine users that know and care nothing about any of this, get their oil changed irregularly, or not at all, and live their lives. If you care about what you drive, like probably most of us on here, I am just throwing this out there. If you want to argue with me, don't. I am not going to.