Just the regular stuff. It makes car tires shine and revitalizes interior vinyl, etc. I've never liked it personally because it attracts dust on car interiors, but it does make tires look good.

There are also several tire-specific products at car stores like Auto Zone. They contain plasticizers specifically designed to nourish and restore tires. Just go down to your local auto parts place and see what they have.

One thing... it would probably be best to re-vitalize the tires before you put them on the your bike. You don't want to get any goop on your rims that might affect braking.

Good luck with it. Sounds like you got a nice deal... and a nice friend.