There's no debating that Mobil1 and Pennzoil products meet or exceed GM specs and are licensed D1G2 products. They are widely available, in brick and mortar, at virtually every garage in the USA and of course online, at very reasonable prices. There's no other oil in the $4/qt range(5qt jugs routinely go on sale for sub$25 at multiple retailers) that's worth the effort to or is able to be argued offers any real advantage other than brand loyalty. (M1 v PP v QSU v CE v ad infinium)
I have very few problems with Amsoil or it's use...You know this. I've advocated it's use numerous times. It's "grouped" together with those because I have a finite amount of time and effort to spend online. It should be clear to virtually all that Amsoil is a different beast. From the price, cost/benefit ratio, to availability at service centers, general brick and mortar, and typical online availability at popular and trusted e-tailers, to actually being licensed(obviously a hotly debated subject....But a concern to many and not a point I mention for any other reason than many other people make it....I know you have X,XXX customers that use it, I've got it in some of my own vehicles as well..)
You can't have a discussion about oil and leave out XMO, SOPUS or Amsoil so they all get mentioned. You also cant negate cost with most people, so the fact that Amsoil averages somewhere between 80% and 200% more expensive than more readily available and licensed options means it's worth offering alternatives to, even if it is arguably the best choice. Especially since I've yet to see a carbon or LSPI related failure in my area on a vehicle run on a steady diet of any "aftermarket" synthetic oil. It's ALWAYS oils that specifically labeled as blends or on bulk ACDelco Dexos
Fuel dilution....Sure you're not wrong. Adjusting OCI to make sure fuel dilution never exceeds 3% is not only expensive and potentially wasteful it is for all reasonable efforts impossible without constant monitoring.
However....That doesn't mean I want to, or advise running around at 4% for 15,000 miles just because it never goes over 4%.
I never said they don't meet or exceed D1G2 specifications; what I'm saying, and have said before, is that it's just not enough.
In fact, I'd argue that bare minimum specifications are rarely, if ever, enough. You are getting exactly what you're paying for; don't fool yourself into believing otherwise just because those companies made better products in the past. I've seen enough of Mobil 1 oxidation and shear stability in recent years that would steer me away from those products for at least five more.
I know you don't have a problem with AMSOIL, and I don't have a problem with pennzoil platinum, but I do have a problem with Mobil 1 based on the test results I have seen.
Even AMSOIL's OE and XL options offer the same LSPI protection claims according to D1G2. Those are claims not repeated by M1 or PP. If they could make those same claims, I'm sure they would, but they're not focused on doing better than the bare minimum required; they're focused on marketing.
I can get you in touch with my buddy Austin whose Malibu dropped a piston on Mobil 1 and was diagnosed as LSPI by the dealer just last year, but I think you trust me enough to not waste my time with that.
OCI has nothing to do with fuel dilution. You can't adjust OCI to make sure fuel dilution never exceeds 3%; you can only adjust your driving conditions (and even then, that's often unreasonable to expect). These higher end oils also handle fuel dilution far better; are able to release it more quickly (from my observations) and are able to continue protecting better while diluted. Fuel dilution is becoming a fact of life; you can't get away from it. If you're scared of 4% fuel dilution, you'd be changing your oil every 500 miles.
I had a lengthy discussion with a technical lead from AMSOIL's development team about this topic and he said that in their testing, the only side effect he's seen with higher fuel dilution is varnish, but it does not affect their recommendations. Furthermore, their reformulation actually removed the "severe service" designation for turbocharged engines. He maintained quite strongly that AMSOIL will protect very well for 15,000 miles in severe service or 25,000 miles for normal service.
I understand this is a bit to wrap your head around given what we are normally comfortable with or exposed to in the American automotive industry, but your hesitation to want or advise running 4% fuel dilution for 15,000 miles, on AMSOIL's signature series,
is simply unfounded.
I really don't want to make this whole thing an AMSOIL sales pitch so I'm trying to remain technical here. I would say this about any oil that had similar capabilities. Take Pennzoil Platinum for example; your biggest issue is going to be oxidation. The fuel (containing ethanol), with short trips (more heat cycles), will introduce more moisture in the crankcase which will be absorbed by the ethanol, which overnight will deplete some of the additives in the oil. That's really your only issue dictating service intervals where fuel dilution exists. If you were running Pennzoil Platinum, for example I would have no reservations changing it at the OEM recommended intervals, with or without fuel dilution.
The biggest thing I'd like you to take away from this discussion is that fuel dilution is not cumulative and can actually reduce over the course of an oil's service life.