If you have Shimano brakes, you need Shimano Mineral Oil. Mineral oil is a generic term, the same as "motor oil", but there's no related SAE specifications, like 5W-30, so it's best to stick within the brand.
There's a small bottle that's ideal for a minor bleed after swapping pads. It's got enough fluid for about 2 full bleeds (3-4 brakes). There's also a 1L bottle that's cheaper per volume, but it's a lifetime supply for anyone other than a shop. The small bottle is enough to get most people started. If you have multiple bikes, then get the jug.
Last edited by gsa103; 10-23-20 at 10:22 AM.