Alan, I have to disagree with you on this one. LC and FP won't mess with an oil's viscosity unless you use a LOT of it, say 16 oz or more of LC per drain.
That fuel percentage is quite high, causing the extra wear and the oil's lower Flash and viscosity ratings. The insolubles are low, so oil filtration isn't much of an issue. Blackstone hit the nail on the head with their comments. Find the source of your fuel dilution, and your problems are solved.
What type of air filter is in this vehicle? I would try another one, even a plain old Fram air filter. Just run GC again with a fresh air filter, resample and take things from there.
Yes, I do agree, changing gas stations may not bea bad idea.