[kjohnson1]

Location: Texas.  Temperature 100+. I stored a sealed gallon of muratic acid outside on a piece of plywood.  On that plywood I also had my pallet jack.  I had recently serviced the pallet jack and spilled some R&O 100 hydraulic oil.  Anyway I happened to be outside and heard a strange noise.  When I investigated, I found a fire where the oil had soaked into the plywood.  What reaction happened here?

Note: Yesterday around this time I smelled burning wood and looked around the entire outside of the house and in the garage.  Perhaps this reaction started a day or more ago and today....resulted in fire.

[Enthalpy]

Welcome, kjohnson1!

Is the acid still sealed?

Hydrochloric acid could hydrolyse wood, but I don't see a path from this cold reaction to flames. With mineral oil, there should be no significant reaction.

Acid would make hydrogen in contact with metals, but hydrogen needs a seriously high temperature to light, like a spark.