i love all eels equally, however experience taught me that tyre tracks are the bad boys of the spiny eel family.
when you buy another eel and add it to a tank with a tyre track the tyre track will "bully" the other eel, especially if the newcomer is smaller that the tyre track.
tyre tracks are territorial and will defend it's teritory. a trick i learned is to remove the tyre track move the decor around then introduce the newcomer and after a couple of days reintroduce the tyre track. this fools them into thinking they are in a new environment and will then be more tollerant of other eels while establising a new territory. this trick works about 65 to 70% of the time.
sometimes you can be lucky and find that the tyre track will tollerate other eels without having to go through the trouble of seprate introductions but that does not happen very often.
i would add the new eel and monitor the tank closely for a day or two, if no sparks fly you were lucky, but if the tyre track is one of the grumpy ones you can try the seperate introduction trick. also just arrange with your lfs to take back the new eel if it does not work out.
good luck with introducing the new eel.
edit: the more places you have in the tank for them to hide the better and it will also help the newcomer to adjust quicker.