Had the misfortune to get Diesel Fuel spilled over Leather Boots.. Looking for a DIY Remedy to remove stain if possible... Thanks

As an owner of several diesel vehicles... there is none I can find.

YOU could try to apply somethiing like mink oil all over them (which will likely darken them) but it will in all likelihood mask the stains you got by in effect staining the entire boots. Taking them to leather specialist might exceed the cost of the boots and not work.