I would idle it too. You could always unplug the vac line from the fuel cutoff and take your keys with you. I've done that before.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine