What is the story of the vanilla ice cream that made General Motors crazy? ?

so the story starts : 

To the engineer’s surprise, the complaint turned out to be true. When the engineer got vanilla ice-cream, the car actually didn’t start. There was nothing left unchecked – the gas used, the car model, the time it took to drive back and forth.Finally, the engineer realized, it took the man a lot longer to buy other flavors of ice-cream. But because vanilla was stored in a different case in the front of the store, it took little time. And this was just the clue he needed.