This was a one gallon jug of standard off-the-shelf kerosene. When I used it all, I refilled the jug with jet-A for easier dispensing into appliances. Few months later, it stunk strongly of vinegar and wouldn't burn well at all in a kero lantern. The 5 gallon can of jet-A I poured it out of also smelled of vinegar, though not as strongly, and it had no residue on the bottom. The residue appears solid and does not flow at all. No cloudiness to the fuel was detected.

Any ideas?

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap