The filaments in Glow plugs are NOT just platinum. Its an alloy of platinum and iridium wire. And plain nichrome glow plugs work for short periods of time. The primary reason ---- as in over 75% of the reason a glow plug engine runs, is because of the sustained engine of combustion from one cycle to the next. The use of platinum simply increases the efficiency to the point of reliability or I should say "acceptable" reliability because of its catalytic properties in the presence of other molecules.

A glow plug engine's principal mode of operation is a filament that sustains heat beyond the combustion cycle into the next combustion cycle that is sufficint to ignite the combustable methanol.
A diesel engines principal mode of operation is based on the fact that compressed gases under Boyles' Ideal Gas law pv=nRT exhibit an exothermic heat release when an extreme pressure on a gas is exerted. Most modern day large Diesel engines no longer use a glow plug.

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http://www.lymanslack.com/ModelAviat...aphy/temp.html

Here’s a brief history of the glow plug as written by SAM Historian Charlie Reich --

Shortly after the war a person named Ed Chamberlin formulated and developed a potent new model engine fuel called "Liquid Dynamite". The fuel testing was done using the Bantam .19 engine. During the test Ed and Ben shut the ignition off, and much to their amazement, the engine kept running. Quickly removing the spark plug they realized that the ground electrode had broken off and the center electrode was glowing red-hot, which

allowed the engine to continue to run using the new hot fuel.
Ben, ever the engineer, experimented and wound small nichrome wire elements to replace the center electrode therein making an early prototype glow plug; however the nichrome material didn't prove successful and burned out very quickly.
During this same time period, Ray Arden was also experimenting with the same Liquid Dynamite fuel on his Arden 19. Ed Chamberlin excitedly advised Ray of his and Ben's discovery. Ray experimented further and discovered that an alloy of platinum and iridium wire provided a superior catalyst for methanol and the modern glow plug was officially born.
Ben Shereshaw made a manufacturing agreement with Ray Arden and Ben thereafter produced millions of glow plugs under the brand name of XL for the OK-Herkimer Company in his Miniature Motors factory.

Arden manufactured his own Glow plugs for a short time until selling his rights to Ben Shereshaw.

Shortly afterwards, O.K of Herkimer, NY also started making glow plugs, and not far behind them, Champion jumped on the bandwagon by introducing their glow plugs in three sizes (VG-2 shown).To my recollection, the first engine to be manufactured specifically for glow (without ignition) was the O.K. Cub .049, a great running little engine.