During WW2 petrol was rationed and many people would store any petrol that was excess to their needs ( rare ) for future use. I recall finding a 44 gallon drum in similar circumstances to pm. I knew from family folklore that it was such petrol. It was yellowish in colour, smelled terrible, could be confused with kero smell but was different. Modern petrol engines would not run on it. It would have been 50 years old.
In those days power kerosine as it was known was coloured green, "lighting"kero ( used in kerosine fridges etc.) was blue.
I was always told that it was illegal to run road vehicles on kerosine, as it was reserved for agriculture, and other industrial uses to aid the war effort. However, many road vehicles were covertly converted to use kero for reasons of cost and availability.
So, could have been either petrol or power kero IMHO.