I guess it is true confession time.

When I first bought my Mercedes I kept looking trough ebay for good deals on stuff I knew I would need some day. I also was not a member of this forum at that time.

During this period I purchased both Autolite and Monark Glow Plugs.

I did not have a Glow Plug Reamer at the time and I insatlled the Autolites.
3 months later I got a Glow Plug Reamer and pulled the Autolites out to Ream the Glow Plug Holes. I had difficulty pulling 2 of the Autolite Glow Plugs out; it turned out those 2 had the tips swollen.

I replaced them with the Monark Glow Plugs and in way over a year I have had no Glow Plug failures. While I do use the Glow plugs when I start it is not Cold here in S. CA.

Since then when they were on sale I bought some Bosch Glow Plugs for use later (made in France).

For a long time I used Champion Glow Plugs in the Volvo with no abnormal failure rate or other problems.
I bought some NKG Glow Plugs on ebay for later use in the Volvo.
They also make Glow Plugs for Mercedes but no one has posted about using any.

So far the Monark GPs are OK. I need to use them up. I do not mind if the fail as long as I can pull them out in a normal manner.
But, the Autolites have the potential to damage your Engine. And, I have see pics on the forum where the tips look like they had exploded.

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84 300D, 82 Volvo 244Gl Diesel