Our 03 sprinter has the original glow plugs and no issues with them at 185K miles.

My 93 190E 2.6 parts car has original spark plugs, distributor, and wires and still runs with 210K miles, although poorly because one of the injectors leaks.

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Current: 1975 450SEL, 83 300D, 88 Yugo GVX, 90 300D OM603 swap, 91 F150 4.6 4v swap, 93 190E Sportline LE 3.0L M104 swap, 93 190E Sportline LE Megasquirt, 03 Sprinter, 06 E500 4Matic wagon.