not in the gas...
I think the quickest way to blow a motor is to add something nasty to the crankcase,not the gas.."Mythbusters" only "plausible" thing added to a gas tank was bleach,that could possibly harm the engine(it made a rusted mess of the gas tank overnight!)...but sugar,paint thiner,draino,and moth balls didn't seem to harm their SBC "test"motor much..
I know if you put super high octane fuel in a motor it can burn valves and melt pistons..one guy I know ran 110 octane aviation fuel in his 400 Pontiac,and it burnt the exhaust valves in a few days of highway driving..
I know of a disgruntled employee at one dealership nearby, that was ticked off about not getting a raise as did his fellow workers..he retaliated by adding a cup full of the metal filings from the brake rotor lathe in the shops service truck...it ran about 20 minutes,and by then,it had NO rod bearings,rings,or pistons in it..seized tighter than a bulls butt in fly season!..they could not even turn it over with a breaker bar to get the torque converter bolts off!..had to pull the tranny with it!..a 2004 Ford,brand new truck with 10,000 miles on it too...

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BTW,a WIX filter is the best there is,or at least ONE of the best..had you said FRAM,I'd agree it might have been the filters that helped cause the meltdown..I have read bad things about Penzoil,but also know guys who won't run anything BUT Penzoil,and have never had any engine failures..boring your motor .080 over was not the best thing to do by any means..I'd lean more toward someone BEATING ON your motors while you were thinking they were safely stored,and doubt it was anything to do with the gas..