The 18th International 500-Mile Sweepstakes Race was held at the Indianapolis Motor Speedway on Friday, May 30, 1930. The race was part of the 1930 AAA Championship Car season.

Pole position winner Billy Arnold took the lead on lap 3, and led the entire rest of the race. He led a total of 198 laps (all consecutive), which stands as an all-time Indianapolis 500 race record. Arnold was accompanied by riding mechanic Spider Matlock.

Arnold was the first driver to complete the entire 500 miles in under five hours (over 100 mph average speed) without relief help. Pete DePaolo finished the 1925 race in under five hours, but used a relief driver for 21 laps. Arnold would eventually be named the first member of the prestigious 100 mph Club.

The race was marred by the death of Paul Marshall. He was acting as riding mechanic for his brother Cy when their car hit and flipped over the wall. His brother survived with serious injuries.

The 1930 race ushered in a series of substantially new engine rules and specifications. The allotted displacement was increased from 91 ¹⁄₂ cu. in. (1.5 L) to 366 cu. in. (6.0 L). Superchargers were banned with the exception of two-cycle engines, and riding mechanics were made mandatory once again. In addition, the traditional mandate of a maximum 33-car field was lifted.

Contrary to popular belief, the rules changes were not made in response to the stock market crash of 1929. The rules package is sometimes referred to disparagingly as the "Junk Formula" or the "Junkyard," and a common misconception is that it was implemented in order to "dumb down" the cars and maintain full fields during the Great Depression.

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Wikipedia