Your truck could still be living despite Lucas, not because of it. That's a possibility that needs to be considered. Or it could be having no effect.
Just as one example: HPL has several different products that all use very high doses of moly. Except their Euro entry line which uses boron instead of moly. Their CEO came right out and said: "we couldn't use moly due to a chemistry clash with the ad pack we're using in the Euro product". So guys who pour Lubeguard into HPL Euro, well at that point they're making the oil perform worse, they're not enhancing it.
Another example, does Lucas contain any silicon? If not, pouring that into something like HPL will reduce the antifoaming properties of the oil. The hemi takes 7 qts, you only give it 6 (or whatever) and fill the rest with Lucas, that means you're reducing the ratio of silicon, and whatever other goodies they got going on to make it a top choice.
There might be cases where an oil is improved with a product like Lucas, but it could just as easily make it worse.
You have some good points, expressing these possibilites as to why or why not and I will say myself the oil it's used with does have an effect.
You are correct it could be doing nothing of benefit or maybe even making things worse.
However with the history I have with it that covers almost 30 years, surely you can understand why I'm not hesitant to use it at all - BTW I will admit 4.3's are known to run for a very long stretch of miles, 300,000 to 400,000 miles with no major problems isn't too uncommon for them as long as you keep up with maintenance due for it.
It's not a matter of simply subbing a quart because you then have too much for the 90/10 ratio to be correct in a Hemi since it holds 7qts (224oz) of oil total when filled..... But if wanting to go with a 85/15 mix ratio, that's about right since 6 quarts is 192oz anyway and 15% of the full 224oz (7qts) is 190.4 oz, that is truly right for stepping it up by 5% on the mix.
I'm not aware of Lucas having stuff like Silicon in it and it does say it does not contain Teflon, Sulphur or Chlorine.
BTW the bottle's directions says to use an 80/20 mix but I believe for engines that run lighter weight oils like 0w-20w,
that's simply too much and using only 10% instead of 20% is a good ratio for engines with such tight tolerances - Which is why I'm only using it as a 90/10 mix rato anyway.
Speaking of foaming:
Additives like Silicon would be diluted by the ratio/amount used (I'd think) so there is definite agreement there.
Oil foaming itself isn't a really big deal
as long as the vehicle is driven often enough, and for long enough each time it's driven to boil out moisture from the oil and from inside the crankcase too.
This foaming/snotty effect is mostly seen on engines/equipment that's kept/stored outdoors and I call it oil "Snot" because that's what it looks like on the stick or under the oil fill cap.
My truck's engine never had oil snot in it because I always drive it enough to boil off moisture that causes oil snot to appear in the first place. Usually about 10-20 miles driven every two weeks is enough to mostly counter the formation of it but that's for here....
Other places may or may not require more runtime because it's mostly due to climate conditions of where the vehicle is and how they change, esp come Springtime which is the worst for it.
If you have it stored indoors it's more manageable BUT that depends if it's in a fully enclosed area or just stuffed in a barn somewhere - Climate controlled storage is always best and will literally stop it from happening.
