Ive got a 20L drum of Kerro that my mate gave me when he drained the old tank down the side of his house.
I use that for washing up in the shed. Its not the best as the dirt tends to suspend in it a bit rather than settle, but its been Ok for cleaning up mower carbs etc (where most of the gunk is from the oil in the fuel).
Ive used diesel before, works Ok too. Diesel and petrol shandy is good as well.
I think most of the commercial parts washers have water in the bottom of the drums, the solids settle in it.
Most of the Truck parts places sell a heavy duty degreaser thats not too expensive. Its pink and class 8. Its nasy on soft girly skin and realy bad in your eyes. Neat it does mean things, its reccomended to dliute it 50:50 with water before using. I use it and a brush and that gets most gunge off. You need to rinse aluminum real well and will have to polish it after as it sort of eats it and leaves a white film on it, same as the HD aluminum cleaner but worse. Ate the paint a bit on one of the mower bases i cleaned up with it.
Reason i mention it is that the best thing for a parts washer is not to wash dirty parts in it
Bob.