I always have a couple of packs of the purple Ideal wirenuts in the truck. When I splice that old soft aluminum building wire I always wire brush and twist the conductors before I apply the connectors.
The major problem with the purple wirenuts is that according to the instructions, they can only be used for aluminum to copper connections, not aluminum to aluminum. So, if you have multiple aluminum wires to splice together in a box, like neutral connections, you need a lot of room for all the individual splices and the final connection for joining all copper conductors together. Very inadequate and quite a pain.
