What do I stuff this pinata with?

I am throwing a retirement party for my brother and need some fun and different ideas to stuff this cement truck pinata. He is a master diesel mechanic who ran the truck shop at a Sand and Gravel place. His interests are cars, trucks and oh, cars! He rebuilds race car carboraters and distributors on the side. He is a funny, witty and a dear. I am trying to make this party really special, he deserves it. Now my other brother, oy!