A method for upgrading vehicle electronic control units (ECUs) in a vehicle comprises: creating a differential upgrade package (DUP) for each upgrade to a predetermined ECU, said creating comprises: comparing a new image of the digital contents of a predetermined ECU flash memory with a present image of the digital contents of the predetermined ECU flash memory; and producing a set of changes to modify the present image to the new image, said changes comprising a set of instructions. The DUP comprises a set of instructions that are utilized to update the ECU flash memory a block at a time.