Factual error: Cameron tries to stop Ferris from borrowing his father's red sports car, explaining that it's an extremely rare and valuable '61 Ferrari 250 GT California. But the car itself is not a real Ferrari. It was manufactured by Modena Design and Development of El Cajon, California, and is a "Modena GT250" which strongly resembles the 1961 Ferrari 250 GT California Spyder. Since the film makers were throwing the car out of a window, using a real Ferrari was 'cost-prohibitive'. Comparing the real Ferrari to the Modena, differences include the Modena's sharper body crease above the grille, the more steeply angled headlamp covers, higher-mounted emblem and counter-sunk hood scoop.
Factual error: The odometer only goes up by 10 miles between the time Cameron freaks out and when they're back in the garage, but they stop at a famous Chicago lighthouse when Cameron freaks out that actually is 1/2 hour outside the city.