Nancy Drew diaries

"Has Nancy Drew solved the world's energy crisis? On a mission sponsored by young, rich, and handsome Ralph Credo, Nancy teams up with eccentric scientist Roy Hinkley to find an amazing high efficiency engine able to operate at an unbelievable 200 miles per gallon! The prototype engine, mounted on a tank, was part of an experiment during the final days of World War II. There's just one problem, the engine and the tank are haunted"--Publisher's web site.