" Even getting a sufficient quantity of crude oil would be difficult to get in that few days."
He could have started with a vat of pig fat if he had been really smart and inventive!
.... TxMike ....

And even if he did, it would be unlikely he could accomplish this in the 5 days he had. Even getting a sufficient quantity of crude oil would be difficult to get in that few days.
Is very bad to steal Jobu's rum. Is very bad.

I know how to make high octane fuel and it isn't very easy, especially in 1885. You'd need catalysts, high-pressure reaction vessels, and a distillation column. I doubt that Doc Brown would even have known the process well enough to know where to start.
.... TxMike ....