How often do you change your spark plugs? I recently changed my spark plugs on my 86 300E after 15,000 miles (1yr). I read a post somewhere on this forum that spark plugs don't need to be changed until after 30,000 miles (2yr). Is this true?

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JR
1986 Gold 300E 4Dr automatic

I removed, applied never-sieze, and replaced the "platinum" spark plugs on my Ford Ranger. They have been firing for 99,000 miles... No problems, even the gap is fine. The plugs in my wagon have been in for 29,000 miles, no problems.
Just thought I'd let you know.

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1992 500SEL 25K
1995 E320 40K
1995 SL600 120K
2002 JX8 Sport 43K
2005 Volvo S40 95K
2006 Isuzu NPR 304K (Frankencamper)
2007 Crown Victoria 150K
2014 Smart Electric 20K

On every car I've serviced in the past 20 years I take the plugs out every 30K (or earlier), grit blast them clean, reset the point, add neversieze, and reinstall. I replace them only if the electrodes start looking really worn, somewhere between 60K and 100K.

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95 E320 Cabriolet, 159K

I have a '91 300E. Since plugs are so easy to change and so cheap to buy, I just arbitrarily change them around 20K. This varies depending on whether or not I'm going on a long trip or about to have an emissions test.

The most difficult thing about changing plugs on the 300E is getting the plug wires off w/o damaging them. I discovered that if you spray the inside of the plug wire boot with HD silicon spray, the wires will pop right off the next time you change plugs.

Bosch copper plugs are pre-gapped and have an anti-seize compound already applied.

Mercedes recommends that plugs be checked at 15K and changed at 30K. These plugs are so cheap and so easy to replace that it's silly to not just pop in a new set.

I change mine every OTHER year in spring when I get a warm day after winter. I use the Bosch copper plugs and they are easy to change and less than a dollar. I use antiseize paste and I have the wire puller. It takes me about a 45 minutes.