Sparkplugs

P, the owner and operator of a Piper Cub airplane, placed an order with D, the owner and operator of an airport service station, to fill the fuel tank of her plane with gas. Dfilled the tank, and P took off. After being airborne for a short time, P's airplane experienced motor failure, requiring a crash landing. P sues D for property damage and personal injuries, alleging that D put automotive rather than aviation gas in the plane, causing the motor failure.

At trial, P's first witness is an aeronautics expert who testifies that one can tell the type of gasoline used in an airplane by the appearance of the sparkplugs and describes the appearance of sparkplugs when automotive gas has been used. P then testifies that following the crash landing she removed the sparkplugs and kept them in her safe deposit box, where they now repose. P's attorney asks her to describe the appearance of the plugs. D objects on grounds of the best evidence rule.

What ruling and why?