Cool stuff, brings back memories... The first oil change I ever did when I was 16, was using that same oil (M1 Tri-Syn) in 10w30... Forgot what it cost me, but I believe it was close to $5 a quart.. That's when brand name conventional sold for about $1.79 a quart.
It went in a 1986 Toyota Tercel 4x4 with the state of the art carbureted 1.5L engine (3A) and all of it's 69 horsepower. At times I think the thing burned more oil than gasoline, so its diet of Mobil1 was short lived.
Later changes consisted of SAE30 or 10w-40 oils to minimize consumption. When an accident finally killed the car it was running on about 2.5 cylinders and had over 250k miles. Just to get up to highway speeds meant shifting at 5-6k rpm. Had to clean the spark plugs regularly of oil deposits in order to keep the few remaining cylinders firing! The horrible compression the engine had yielded about 14 miles per gallon mixed city/highway.