Unfortunately there is no adequate way to test the quality of Glow Plugs but to put them in your Engine and use them.

Being American made has not helped the Autolite Glow Plugs for Mercedes as far as quality is concerned.

It would be nice to have another choice.

One of the internets part sellers sells the Bosch Glow Plugs for less than $9 each. The last time I bought some they were made in France.

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84 300D, 82 Volvo 244Gl Diesel