Leather likes oil, it helps condition and protect the leather. If you wash oils out of the leather you will need to replace it.
Instead of trying to wash out the areas that have some Canola oil on them, oil the entire boot with Canola oil.
There are several references on line suggesting the Canola oil (or other vegetable oils) is a good product for the job. Though some suggest not using it on horse items, as it may encourage rats in the barn to nibble on the leather. I did not find evidence this was true, put did find references of people use it on horse items.
Wipe the vegetable oil over the top of the leather items that are clean and dry, applying a thin layer of vegetable oil to the leather. Source
For oil, we use Olive Oil. We buy it from a local grocery supply company by the case and use it on both new and used leather items. I have heard of many people using canola, peanut, vegetable, and other food oils and they seem to work fine. Source
Note: Suede and Nubuck leather will not look as fluffy, if they are oiled. As these are work boots, I am assuming that a consistent oiled look, will be acceptable.